Air conditioner with refrigerant r134a_Audi TT_Type_8J_MK2_he thong dieu hoa

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Introduction

This manual is intended to provide foremen and mechanics with the basic knowledge needed to ensure reliable and successful repairs.

Thoroughly studying the manual and receiving appropriate training on automotive air conditioning systems, including any necessary qualification tests, is essential for effectively applying the gained knowledge in practical situations.

This document is a compact reference work which should be kept at the workplace It should also be available for presentation to the responsible supervisory agency on request.

Other reference material

For model-specific servicing, refer to the workshop manual focusing on heating and air conditioning (Repair Group 87) This manual includes vehicle-specific guidelines, current flow diagrams, electrical fault finding procedures, and fitting locations to ensure efficient maintenance and troubleshooting of HVAC systems.

♦ Technical Service Handbook (TPI) outlining action to be taken to rectify current problems

♦ Self-study programmes, e.g ⇒ Self-study programme No

208 ; Air conditioning systems in motor vehicles

♦ Video training courses for dealerships

♦ List of special tools and workshop equipment required for servicing air conditioning systems ⇒ Workshop equipment catalogue

♦ Service Organisation Handbook, Vol „1“ „Additional equip‐ ment“ ⇒ Audi ServiceNet, Handbooks

♦ Air conditioner with refrigerant R12 Workshop Manual (for ve‐ hicles manufactured up to model year 1993; this Workshop

Manual is available in hardcopy form only)

Principles of air conditioning systems

♦ Pressure and boiling point ⇒ page 2

♦ Vapour pressure table for refrigerant R134a ⇒ page 3

The four familiar states of water apply to air conditioning refriger‐ ants, too.

When water is heated in a vessel, it absorbs heat and produces visible water vapor Continued heat absorption transforms this vapor into an invisible gas This process is reversible; when heat is removed from the gaseous water, it first condenses into vapor, then into liquid water, and finally freezes into ice.

Heat always flows from a warmer to a colder substance

Every substance is made up of moving molecules, and when warmer substances transfer energy to cooler ones, the faster molecules slow down while the slower molecules speed up This energy exchange continues until both substances reach the same molecular motion, indicating they are at the same temperature, at which point no further heat transfer occurs.

The boiling point given in tables for a liquid is always referenced to an atmospheric pressure of 1 bar If the pressure acting on a

Pressure is measured in various units, with 1 MPa (megapascal) equating to 10 bar gauge pressure or 145 psi Additionally, 1 bar of absolute pressure corresponds to 0 bar gauge pressure, which is approximately equal to atmospheric pressure.

For example, the lower the pressure, the lower the temperature at which water boils.

The vapor pressure curves for water and refrigerant R134a illustrate that decreasing temperature at a constant pressure leads to the conversion of vapor to liquid in the condenser, while lowering pressure results in the refrigerant transitioning from liquid to vapor in the evaporator.

Vapour pressure curve for water

C - Vapour pressure curve for water

1 - Pressure acting on liquid in bar (absolute)

Vapour pressure curve for refrigerant R134a

D - Vapour pressure curve for refrigerant R134a

1 - Pressure acting on liquid in bar (absolute)

1.3.3 Vapour pressure table for refrigerant

The vapour pressure table for refrigerants is essential for refrigeration system engineers, as it allows them to ascertain the vapour pressure exerted on the liquid column in a vessel based on its temperature.

As there is a known characteristic vapour pressure table for every refrigerant, the type of refrigerant can be identified by way of pressure and temperature measurement.

At absolute pressure, "0 bar" signifies a complete vacuum, while normal atmospheric pressure is represented as "1 bar" absolute pressure Most pressure gauges indicate "0 bar" as an absolute pressure of 1 bar, often shown as "-1 bar" below the zero mark.

Pressure can be measured in different units, where 1 MPa (megapascal) equals 10 bar gauge pressure or 145 psi Additionally, 1 bar absolute pressure is equivalent to 0 bar gauge pressure, which is approximately the same as atmospheric pressure.

Temperature in °C Pressure in bar (gauge pres‐ sure), R134a

Refrigerant R134a

Vehicle air conditioning systems make use of the vaporisation and condensation process These systems employ a substance with a low boiling point, referred to as refrigerant.

The refrigerant used is tetrafluoroethane R134a, which boils at

-26.5°C at a vapour pressure of „1 bar“.

♦ Environmental aspects of refrigerant R134a ⇒ page 5

Chemical formula CH2F–CF3 or CF3–CH2F

The critical point (critical temperature and critical pressure) is that above which there is no longer a boundary between liquid and gas.

A substance above its critical point is always in the gaseous state.

At temperatures below the critical point, all types of refrigerant in pressure vessels exhibit both a liquid and a gas phase, i.e there is a layer of gas above the liquid.

As long as both liquid and gas are present in the vessel, the pres‐ sure is governed by ambient temperature ⇒ page 3 „Vapour pressure table“.

Different types of refrigerant must never be mixed The refrigerant specified for the respective air conditioning system must be used exclusively.

♦ R134a is a fluorocarbon and contains no chlorine.

♦ R134a has a shorter atmospheric lifespan than refrigerant

♦ R134a does not damage the ozone layer, the ozone depletion potential is zero.

♦ The global warming potential (GWP) of R134a is 1300 (the

♦ The global warming effect of R134a is ten times less than that of refrigerant R12.

Properties of refrigerant R134a

♦ Trade names and designations ⇒ page 6

♦ Critical temperature/critical pressure ⇒ page 6

The refrigerant R134a is currently available under the following trade names:

♦ Different trade names may be used in other countries.

♦ Of the wide range of refrigerants available, this is the only one which may be used for vehicles The designations Frigen and

Freon are trade names They also apply to refrigerants which should not be used in vehicles.

Refrigerants, like water, are colorless in both their vapor and liquid states, with the gas remaining invisible The only visible aspect is the boundary layer between the gas and liquid, which can be seen in the indicator tube of a charging cylinder or as bubbles in a sight glass While liquid refrigerant R134a may appear milky in a sight glass, this cloudiness is due to partially dissolved refrigerant oil and does not signify any malfunction.

In a closed vessel with a partial refrigerant fill, the amount of refrigerant vaporizing matches the amount condensing back into liquid, achieving a state of equilibrium known as vapor pressure This vapor pressure is influenced by temperature and pressure conditions.

As the vapour pressure curves of R134a and other refrigerants are sometimes very similar, unequivocal identification cannot be made simply on the basis of pressure.

When using R134a, the air conditioner compressor is lubricated by means of special synthetic refrigerant oils, e.g PAG oils (pol‐ yalkylene glycol oils).

In its pure state, refrigerant R134a is chemically stable and does not corrode iron or aluminium.

Contamination of refrigerants, particularly with chlorine compounds, can cause corrosion in metals and plastics, leading to potential blockages, leaks, or deposits in the air conditioner compressor piston.

The refrigerant R134a remains chemically stable up to a gas pressure of 39.5 bar (corresponding to a temperature of 101 °C).

Above this temperature, the refrigerant decomposes (refer to

Only very small amounts of water are soluble in liquid refrigerant.

On the other hand, refrigerant vapour and water vapour mix in any ratio.

Even a small amount of water, around 7 grams, in the refrigerant circuit can lead to significant issues Once the dryer in the receiver absorbs this moisture, it can become entrained in droplet form, traveling to the expansion valve nozzle or restrictor There, the water freezes, causing the air conditioner to lose its cooling effect entirely.

Water causes irreparable damage to the air conditioner because at high pressures and temperatures it combines with other im‐ purities to form acids.

Refrigerant is a non-flammable substance that possesses fire-inhibiting properties, effectively extinguishing flames However, it can decompose when subjected to flames or high temperatures, as well as UV light generated during processes like electric welding This decomposition produces toxic byproducts that should not be inhaled.

However, these chemicals irritate the mucous membranes, giving adequate warning of their presence.

A vessel must accommodate both vapor and liquid; as temperature increases, the liquid expands, reducing the vapor space Eventually, the vessel contains only liquid, and any further temperature rise leads to significant pressure buildup, as the liquid tries to expand without sufficient space.

Excessive resultant forces can cause a vessel to rupture, which is why regulations for storing compressed gases limit the amount of refrigerant allowed per litre of internal vessel volume The maximum allowable capacity is determined by multiplying the vessel's internal volume by a specified "charge factor."

The figure for the refrigerant used in motor vehicles is 1.15 kg/ litre.

External damage can lead to leaks in the refrigerant circuit, allowing small amounts of refrigerant to escape These minor leaks can be identified using an electronic leak detector or by adding a leak detection additive to the refrigerant system.

Electronic leak detectors are capable of registering leaks with re‐ frigerant losses of less than 5 g per year.

Use must be made for the various refrigerants of leak detectors designed for the composition of the refrigerant concerned For example, a leak detector for R12 refrigerant is not appropriate for

R134a, as R134a refrigerant has no chlorine atoms and the leak detector therefore does not respond.

Refrigerant oil

Refrigerant oil mixes with the refrigerant (about 20 - 40 %, de‐ pending on compressor type and amount of refrigerant) and circulates constantly in the system, lubricating the moving parts.

Special synthetic refrigerant oils, e.g polyalkylene glycol (PAG) oil, are used in conjunction with R134a air conditioning systems.

This is necessary as mineral oil, for example, does not mix with

R134a air conditioning systems may experience corrosion due to high-pressure refrigerant flow and elevated temperatures, which can compromise the integrity of the materials Additionally, the breakdown of the lubricating film in the compressor can lead to system failure To prevent these issues, it is essential to use only approved oils, as the use of non-compliant oils can severely damage the air conditioning system.

Type of oil for R134a in motor vehicles: PAG (polyalkylene glycol)

♦ Do not store refrigerant oils in open containers as they are extremely hygroscopic (water-absorbing).

♦ Always keep oil containers sealed.

♦ Do not re-use old refrigerant oil It must be disposed of as used oil of unknown origin ⇒ Audi-ServiceNet, HSO Environmental

♦ Ester-based oils are only intended for use with large systems

(not for motor vehicle air conditioners).

♦ Properties of refrigerant oil ⇒ page 8

Key properties of refrigerant oils include high solubility with refrigerants, excellent lubricity, a lack of acidity, and minimal water content Consequently, only specific oils are approved for use For a comprehensive list of approved refrigerant oils and their capacities, please refer to the relevant guidelines.

PAG oils, specifically designed for R134a refrigerants, are highly hygroscopic and incompatible with other oils To prevent moisture absorption, it is crucial to reseal opened containers immediately The presence of moisture and acids accelerates the degradation of refrigerant oil, leading to darkening, increased viscosity, and corrosion of metal components.

Due to its unique chemical properties, refrigerant oil should not be mixed with engine or gear oil during disposal It must be treated as used oil of unknown origin, as recommended by Audi.

♦ Only oil approved for the air conditioner compressor is to be used for refrigerant circuits containing refrigerant R134a ⇒

Electronic parts catalogue and capacities ⇒ page 164

How air conditioning works

The temperature inside a vehicle's passenger compartment is influenced by the heat entering through the windows and being conducted by the metal body In hot weather, it is essential to remove some of this heat to create a more comfortable environment for passengers.

In the passenger compartment, a cooling unit generates low temperatures by continuously evaporating refrigerant, extracting heat from the air passing through the evaporator The air conditioner's compressor then raises the temperature and heat content of the refrigerant, resulting in a temperature significantly higher than that of the surrounding air.

The hot refrigerant transfers its heat to the condenser, where it releases this heat to the surrounding air, driven by the temperature difference between the refrigerant and the ambient environment.

The refrigerant thus acts as a heat transfer medium As it is reused, the refrigerant is returned to the evaporator.

For this reason all air conditioning systems are based on the re‐ frigerant circulation principle There are however differences as regards the units used.

♦ Comfort of vehicle occupants ⇒ page 9

Comfort in the passenger compartment is essential for concentration and safe driving, particularly in hot and humid conditions where air conditioning is crucial While opening windows or the sunroof can enhance comfort and increase airflow, these actions may introduce drawbacks such as increased noise, drafts, exhaust fumes, and unfiltered pollen, which can be bothersome for allergy sufferers.

Effective climate control, combined with a well-designed heating and ventilation system, enhances passenger comfort and wellbeing by optimizing temperature, humidity, and air circulation This regulation adapts to ambient conditions whether the vehicle is stationary or in motion.

Other important advantages of air conditioning:

♦ Purification of the air supplied to the passenger compartment

(dust and pollen, for example, are washed out by the moist fins of the evaporator and removed with the condensate).

♦ Temperatures in a mid-size car (example: after short travelling time, ambient temperature 30 °C in the shade and vehicle ex‐ posed to sunlight).

With air conditioning Without air condi‐ tioning

Since about 1992, the air conditioning systems of newly manu‐ factured cars have been successively changed to refrigerant

R134a This refrigerant contains no chlorine and therefore does not deplete the ozone layer.

Until about 1992, R12 refrigerant was commonly used in air conditioning systems However, due to its chlorine content, this CFC contributed significantly to ozone depletion and had the potential to exacerbate the greenhouse effect.

Conversion programs are offered for outdated systems that utilize the ozone-depleting refrigerant R12 A comprehensive Workshop Manual for air conditioners using R12 is available exclusively in hardcopy format.

For environmental reasons, refrigerants must not be released into the atmosphere ⇒ page 40 (see the relevant environmental leg‐ islation).

General work safety

♦ In accordance with regulations of the German industrial liabil‐ ity insurance association, VBG 20, (other regulations may apply in other countries)

♦ Heed the workplace-specific instructions ⇒ Audi-ServiceNet,

HSO Environmental Protection , which are to be displayed at refrigerant workplaces.

Product properties

Refrigerants utilized in automotive air conditioning systems are part of a new generation that features chlorine-free, partially fluorinated hydrocarbons, such as H-FKW and R134a, which may be referred to by different names in various countries.

Refrigerants are substances that have been liquefied under pressure and possess specific physical properties Due to their nature, they are regulated as pressure vessels and must be utilized only in approved and correctly labeled containers.

Specific requirements must be observed to ensure safe and prop‐ er handling:

Handling refrigerant

If refrigerant vessels are opened, the contents may escape in liq‐ uid or vapour form The higher the pressure in the vessel, the more vigourous the process.

The pressure level is governed by two factors:

• The type of refrigerant in the vessel „Rule: The lower the boil‐ ing point, the higher the pressure.“

• The temperature level „Rule: The higher the temperature, the higher the pressure.“

♦ Do not open vessels containing refrigerant.

Put on safety goggles to prevent refrigerant getting into the eyes, as this could cause severe injury through frostbite.

Wear protective gloves and apron

Refrigerants can easily dissolve grease and oils, which can harm the protective layer of grease on the skin Consequently, degreased skin becomes more vulnerable to cold temperatures and germs.

Do not allow liquid refrigerant to come into contact with the skin

The refrigerant absorbs heat for evaporation from its surroundings, including the skin, which can lead to dangerously low temperatures and potential local frostbite The boiling point of R134a is a critical factor in this process.

Do not inhale refrigerant vapours

If refrigerant vapour escapes in concentrated form, it mixes with the surrounding air and displaces the oxygen necessary for

A burning cigarette can cause refrigerant to decompose The re‐ sultant substances are toxic and must not be inhaled.

Welding and soldering on refrigeration systems

Before starting any welding, brazing, or soldering on vehicles near air conditioning components, it is essential to extract the refrigerant and thoroughly purge any residual refrigerant using nitrogen.

Decomposition of refrigerants due to heat produces toxic and highly corrosive byproducts, primarily hydrogen fluoride, which can severely damage pipes and system components.

A strong odor signifies the presence of harmful decomposition products It is crucial to avoid inhaling these substances, as they can cause damage to the airways, lungs, and other organs.

• Following accidental contact with eyes or mucous mem‐ branes, immediately rinse with copious amounts of running water and consult an eye specialist.

• Following accidental contact with the skin, immediately re‐ move clothing affected and rinse skin with copious amounts of water.

In the event of accidental inhalation of concentrated refrigerant vapors, promptly move the affected individual to fresh air and seek medical assistance If they experience breathing difficulties, provide oxygen For severe breathing issues or if the person is not breathing, tilt their head back and perform artificial respiration.

Handling pressure vessels

Secure vessels to prevent them falling over.

Secure upright cylinders to stop them falling over and cylinders lying flat to stop them rolling away.

Pressure vessels must never be thrown.

If dropped, the vessels could be so severely deformed that they rupture The refrigerant evaporates immediately, liberating con‐ siderable force Flying fragments of cylinders can cause severe injuries.

To protect the valves, cylinders may only be transported with the protective cap screwed on.

Valves may break off if cylinders are not properly transported.

Never store in the vicinity of radiators.

High temperatures may occur in such areas High temperatures are also accompanied by high pressures and the maximum per‐ missible vessel pressure may be exceeded.

To avoid possible risk, pressure vessel regulations specify that vessels are not to be heated to in excess of 50 °C.

Do not heat in an uncontrolled manner

Avoid using a naked flame for heating, as localized overheating can alter the vessel's material structure, compromising its pressure resistance Additionally, there is a risk of refrigerant decomposition caused by such overheating.

To prevent moisture from entering empty refrigerant vessels, it is essential to keep them sealed Moisture can lead to rusting of steel containers, which compromises the integrity of the vessel walls Furthermore, rust particles that enter refrigeration systems from these storage vessels can result in malfunctions.

Safety regulations for working with extraction and charging systems

• Before connecting the charging system to the air conditioning system, ensure that the shut-off valves are closed.

• Before disconnecting the charging system from the air condi‐ tioning system, ensure that the process has been completed so that no refrigerant can escape into the atmosphere.

• Once the purified refrigerant from the charging system has been transferred to an external compressed-gas cylinder, close the hand shut-off valves at the cylinder and charging system.

• Do not expose the charging system to moisture or use it in a wet environment.

• Disconnect from power supply before performing service work on the charging system.

Using an extension cable is generally discouraged due to the increased risk of fire hazards However, if it's necessary to use one, ensure that the minimum cross-section of the cable is 2.5 mm² for safety.

• In case of fire, remove external cylinder.

Entrained oil from the air conditioning system is collected by the suction unit into a measurement vessel This oil must then be transferred to a sealable container, as it contains a small amount of refrigerant that should not be released into the environment.

• Following shutdown, the air conditioner service station must be secured to stop it rolling away.

Safety measures for working on vehicles with air conditioning system and for handling

cles with air conditioning system and for handling refrigerant R134a

♦ It is advisable to keep an eye bath to hand.

♦ Should liquid refrigerant come into contact with the eyes, rinse them thoroughly with water for about 15 minutes.

Then administer eye drops and consult a doctor immedi‐ ately even if no pain is felt.

It is crucial to inform the doctor that the frostbite resulted from refrigerant R134a exposure If refrigerant contacts other body areas, even when safety regulations are followed, those areas should be rinsed thoroughly with cold water for about 15 minutes.

♦ Work may only be performed on the refrigerant circuit of an air conditioning system in well ventilated areas Switch on workshop extraction systems, if available.

♦ Refrigerant must not be stored in low-level areas (e.g cel‐ lars) and their exits or light wells.

Welding, brazing, and soldering on air conditioning system components should never be done while they are charged, including during vehicle repairs where there's a risk of overheating Additionally, when conducting paintwork repairs, it's crucial to ensure that the temperature in the drying booth or preheating zone remains below 80 °C to prevent damage.

Exposure to heat gives rise to considerable pressure in the sys‐ tem, which could cause the pressure relief valve to open.

– Discharge refrigerant circuit using air conditioner service sta‐ tion.

Damaged or leaking components of the air conditioning system are not to be repaired by welding or soldering They must always be replaced.

Refrigerant vessels (e.g charging cylinders of air conditioner service station) must never be subjected to excessive heat or ex‐ posed to direct sunlight.

– Vessels must never be completely filled with liquid refrigerant.

Without sufficient room for expansion (gas cushion), vessels will rupture with explosive effect in the event of an increase in temperature ⇒ page 5

Refrigerant should never be poured into systems or vessels con‐ taining any air.

– Evacuate systems and containers before charging with refrig‐ erant.

Basic rules for working on refrigerant circuit

♦ Additionally for vehicles with air conditioner compressor with no magnetic clutch (with air conditioner compressor regulating valve -N280- ) ⇒ page 15

• Heed the workplace-specific instructions ⇒ Audi-ServiceNet,

• Ensure absolute cleanliness when working.

• Wear safety goggles and gloves when working with refrigerant and nitrogen.

• Switch on workshop extraction systems, if available.

• Always use air conditioner service station to discharge refrig‐ erant circuit, then unfasten screw connections and renew defective components.

• Use caps to seal off opened assemblies and hoses to prevent the ingress of moisture and dirt.

• Use only tools and materials intended for refrigerant R134a.

• Seal opened refrigerant oil containers to protect against mois‐ ture.

♦ After completing service work, screw sealing caps (with seals) onto all connections with valves and service connections.

♦ Before starting up the air conditioning system, heed the vehi‐ cle-specific capacities ⇒ page 144

♦ Do not top up refrigerant in circuit; discharge existing refriger‐ ant and re-charge system.

The refrigerant circuit must be flushed out with refrigerant R134a

⇒ page 59 (or blown out with compressed air and nitrogen

⇒ page 55 ) in the following cases:

– If moisture or dirt has ingressed into the refrigerant circuit (e.g. following an accident).

– If the refrigerant oil is dark and viscous.

– If there is too much refrigerant oil in the refrigerant circuit after compressor replacement.

– If the air conditioner compressor has to be replaced on ac‐ count of „internal“ damage (e.g noise or no output).

When blowing out components with compressed air and nitrogen, always extract the gas mixture escaping from the components with suitable extraction units (workshop extraction system).

1.14.3 Additionally for vehicles with air condi‐ tioner compressor with no magnetic clutch (with air conditioner compressor regulating valve -N280- )

• The engine is only to be started following complete assembly of the refrigerant circuit (constant air conditioner compressor operation).

• If the engine has to be operated with the refrigerant circuit empty, only do so for as long as absolutely essential and avoid high engine speeds.

♦ Make exclusive use of seals which are resistant to refrigerant

R134a and the related refrigerant oils Colour coding of O-ring seals is no longer employed Black and coloured O-rings are used.

♦ Pay attention to the correct inside diameter of the seals used

⇒ Electronic parts catalogue , ⇒ Heating, air conditioning;

Rep gr 87 and / or ⇒ Air conditioning; Rep gr 87 (vehicle- specific workshop manual).

♦ Seals may only be used once.

♦ Before fitting, moisten seals slightly with refrigerant oil (PAG oil).

Before using air conditioner after system has been re-charged

– Give the air conditioner compressor approx 10 turns by hand by way of the magnetic clutch plate or the pulley.

– Start the engine with the air conditioning system switched off

( air conditioning system magnetic clutch -N25- and air condi‐ tioner compressor regulating valve -N280- are not actuated).

– Switch on the air conditioner compressor once the idling speed has stabilised and run it for at least 10 minutes at idle in the maximum cooling output setting.

2 General information on refrigerant circuit

♦ Components of refrigerant circuit ⇒ page 16

♦ Arrangement of the refrigerant circuit components and their influence on the high and low-pressure ends ⇒ page 16

♦ Design of refrigerant circuit ⇒ page 25

♦ Connections for quick-release coupling in refrigerant circuit

♦ Switches and senders in refrigerant circuit and related con‐ nections ⇒ page 28

♦ Electrical components not fitted in the refrigerant circuit

♦ Pressures and temperatures in refrigerant circuit

♦ Test and measurement operations which can be performed with a pressure gauge ⇒ page 37

♦ Air conditioner service and recycling units ⇒ page 38

♦ Repair notes for refrigerant circuit ⇒ page 39

Components of refrigerant circuit

• All components of the refrigerant circuit submitted for quality observation are always to be sealed (use the original sealing caps of the replacement part).

• Renew damaged or leaking components of refrigerant circuit

The replacement parts for the air conditioning system, including the compressor, reservoir, evaporator, and condenser, have been filled with nitrogen gas, but this practice is being phased out As a result, there is minimal to no noticeable pressure equalization when the sealing plugs are removed from these components.

Arrangement of the refrigerant circuit components and their influence on the high and low-

components and their influence on the high and low-pressure ends

High-pressure end: Condenser, receiver and restrictor or expan‐ sion valve to separate the high and low-pressure liquid ends.

High pressure results from the restrictor or expansion valve form‐ ing a constriction and causing the refrigerant to accumulate, thus leading to an increase in pressure and temperature.

Excess pressure in a refrigeration system can arise from several factors, including an overabundance of refrigerant or oil, contamination of the condenser, a malfunctioning radiator fan, blockages within the system, or moisture present in the refrigerant circuit, which can lead to icing in the restrictor or expansion valve.

Low-pressure end: Evaporator, evaporator temperature sensor and air conditioner compressor to separate the high and low- pressure gas ends.

A drop in system pressure can be caused by a loss of refrigerant, the restrictor or expansion valve (constrictions), a defective air

♦ Refrigerant line with internal heat exchanger ⇒ page 22

♦ Quick-release couplings on refrigerant line ⇒ page 23

♦ Pipes and hoses of refrigerant circuit ⇒ page 24

The air conditioner compressor is driven by the engine via a poly

Air conditioner compressor with magnetic clutch:

An electromagnetic clutch connects the air conditioner compressor to the pulley, enabling power transfer when the air conditioning system is activated.

Air conditioner compressor with no magnetic clutch:

An overload safeguard connected to the pulley or installed in the drive unit of the air conditioner compressor activates to protect the belt drive from overload when the compressor is not operating smoothly.

The air conditioner compressor draws in refrigerant gas from the evaporator, compresses it and conveys it to the condenser.

♦ The air conditioner compressor contains refrigerant oil which mixes with refrigerant R134a at all temperatures.

♦ The rating plate indicates the refrigerant for which the air con‐ ditioner compressor is designed A valve regulates the pres‐ sure on the low-pressure side within the specified range

♦ A regulating valve is actuated externally on air conditioner compressors with no magnetic clutch.

♦ On air conditioner compressors with no magnetic clutch, the engine is only to be started following complete assembly of the refrigerant circuit.

To avoid damage to the air conditioner compressor when the refrigerant circuit is empty, the magnetic clutch is turned off, and the air conditioner compressor regulating valve -N280- is not activated, causing the compressor to idle with the engine.

When the refrigerant circuit is empty, the air conditioner compressor, which lacks a magnetic clutch, switches to internal lubrication through a valve.

Air conditioner compressors may feature a valve on the high-pressure end to prevent liquid refrigerant backflow after the system is turned off In vehicles equipped with a refrigerant circuit that includes an expansion valve, this setup can lead to a prolonged period before high-pressure levels drop When the system is off, the expansion valve remains cold, causing rapid pressure increases on the low-pressure side, which eventually leads to the valve closing and slow refrigerant flow to the low-pressure end However, when the compressor is activated, the low-pressure side pressure decreases, prompting the expansion valve to open and allowing refrigerant to flow efficiently.

The condenser dissipates heat from the compressed refrigerant gas to the surrounding air.

During this process, the refrigerant gas condenses to form liquid.

The design of the refrigerant circuit determines whether the receiver is attached to or integrated into the condenser This configuration is crucial for systems used in heating and air conditioning, as detailed in the vehicle-specific workshop manual for air conditioning (Rep gr 87).

The liquid refrigerant evaporates within the coiled pipes of the evaporator, absorbing heat from the air that flows over the evaporator fins This process cools the air, while the refrigerant, now in vapor form, is drawn into the air conditioner compressor along with the heat it has absorbed.

A specific amount of refrigerant is delivered to the evaporator through a restrictor or expansion valve, ensuring optimal performance In systems equipped with an expansion valve, the flow rate is carefully controlled, allowing only gaseous refrigerant to exit the evaporator outlet.

To optimize the air conditioning system, the reservoir is designed to collect the mixture of vapor and gas from the evaporator, ensuring that only gaseous refrigerant is drawn into the compressor This process effectively converts vapor into gaseous refrigerant, enhancing the system's efficiency.

Refrigerant oil entrained in the circuit does not remain in the res‐ ervoir as an oil extraction hole is provided.

Any moisture ingressing into the refrigerant circuit during assem‐ bly is trapped by a filter (desiccant bag) in the reservoir.

Gaseous refrigerant with oil is drawn in by the air conditioner compressor.

♦ Renew reservoir if refrigerant circuit has been open for a rel‐ atively long period and moisture has ingressed, or if replace‐ ment is stipulated due to a specific complaint ⇒ page 136

♦ Do not remove the sealing plugs -A- and -B- until immediately prior to installation.

♦ If the reservoir is not sealed, the desiccant bag soon becomes saturated with moisture and thus unusable.

♦ When installing, observe arrow indicating direction of flow (if applicable).

The restrictor creates a constriction that divides the refrigerant circuit into high and low-pressure sections, resulting in warm refrigerant upstream and cold refrigerant downstream To ensure optimal performance, a strainer is installed upstream to capture dirt, while a downstream strainer atomizes the refrigerant before it enters the evaporator.

♦ Arrow -A- on restrictor faces evaporator.

♦ Always replace after opening the circuit.

♦ Different versions exist; heed the applicable notes in the var‐ ious service information booklets ⇒ Heating, air conditioning;

Rep gr 87 or ⇒ Air conditioning; Rep gr 87 (vehicle-specific workshop manual) and ⇒ Electronic parts catalogue

The receiver gathers liquid droplets and transports them continuously to the expansion valve, while a dryer within the receiver captures any moisture that may enter the refrigerant circuit during assembly.

♦ Renew receiver if refrigerant circuit has been open for a rela‐ tively long period and moisture has ingressed, or if replace‐ ment is stipulated due to a specific complaint ⇒ page 136

♦ Do not remove the sealing plugs until immediately prior to in‐ stallation.

♦ If the receiver is not sealed, the desiccant bag soon becomes saturated with moisture and thus unusable.

♦ When installing, observe arrow indicating direction of flow (if applicable).

The design of the refrigerant circuit can determine whether the receiver is integrated with the condenser or installed separately This configuration is relevant for heating and air conditioning systems, as well as for vehicle-specific workshop manuals and electronic parts catalogs.

The approach to resolving issues varies based on the type of receiver/dryer cartridge When the receiver is connected to the condenser, both components can be replaced simultaneously However, if the receiver is built into the condenser, the dryer cartridge and any additional filter can typically be replaced independently.

If the receiver is built into the condenser and cannot be replaced independently, it may be necessary to replace the entire condenser unit This applies to heating and air conditioning systems, categorized under repair group 87 or air conditioning repair groups.

87 (vehicle-specific workshop manual) and ⇒ Electronic parts catalogue

Design of refrigerant circuit

♦ Refrigerant circuit with expansion valve and evaporator

♦ Refrigerant circuit with restrictor and reservoir ⇒ page 25

2.3.1 Refrigerant circuit with expansion valve and evaporator

3 - Valve for extraction, charging and measurement

4 - Sight glass (not fitted with R134a circuits)

Arrows show direction of refrigerant flow.

2.3.2 Refrigerant circuit with restrictor and reservoir

Connections for quick-release coupling in refrigerant circuit

• Only valves and connections resistant to R134a refrigerant and the related refrigerant oils are to be used.

• There are different connections (outer diameter) for high and low-pressure sides.

• Discharge refrigerant circuit before removing valves or valve cores.

• Always screw on sealing caps.

Layout in vehicle ⇒ Heating, air conditioning; Rep gr 87 or ⇒

Air conditioning; Rep gr 87 (vehicle-specific Workshop Manual).

♦ Connections with Schrader valve (needle valve) ⇒ page 26

♦ Connections with primary sealing valve (ball valve)

2.4.1 Connections with Schrader valve (nee‐ dle valve)

♦ -B- Valve core (designation: Schrader valve or needle valve)

After establishing the connection, securely tighten the handwheel of the service coupling into the quick-release coupling adapter until the valve in the service connection opens sufficiently Monitor the pressure gauge closely to avoid overextending the valve.

♦ To remove and install the valve core -B- with the refrigerant circuit drained, make use of an adapter from the socket -

♦ Take care when tightening valve core -B- (low torque).

♦ There are different versions of these valves and the tightening torques therefore also differ The tightening torque for a valve insert -B- with a VG5 thread (5.2 x 0.7 mm, tyre valve) is

0.4 Nm +- 0.1 Nm For a valve insert with an M6 x 0.75 mm thread, the tightening torque is 0.9 Nm +- 0.1 Nm and for a valve insert with an M8 x 1.0 mm thread it is 2.0 Nm +- 0.2 Nm.

Different versions of valve cores and their corresponding sealing caps exist, making it crucial to ensure the correct type of valve core is used along with the appropriate sealing cap For detailed specifications, refer to the electronic parts catalogue.

2.4.2 Connections with primary sealing valve

Before unscrewing connection, connect air conditioner service station and extract refrigerant The refrigerant circuit must be empty; danger of injury.

Connection with high-pressure valve

1 - Connection with internal thread (soldered in)

2 - O-ring (version and identification: black or coloured ⇒ Elec‐ tronic parts catalogue )

3 - Valve with external thread and groove for O-ring (designa‐ tion: Ball valve)

After establishing the connection, securely tighten the handwheel of the service coupling into the quick-release coupling adapter until the valve in the service connection opens sufficiently Monitor the pressure gauge closely to ensure the valve is not overextended.

♦ To remove and install the valve -3- with the refrigerant circuit drained, make use of an adapter from the socket -T10364- for example.

Various valve versions exist, featuring either internal or external threads, which can result in differing tightening torques Currently, the tightening torque for valves with an M12 x 1.5 mm external thread is set at 9 Nm ± 1 Nm.

Different versions of valves and their corresponding sealing caps exist, making it essential to ensure the correct valve version is matched with the appropriate sealing cap.

Connection with low-pressure valve

1 - Connection with external thread and groove for O-ring (sol‐ dered in)

2 - O-ring (version and identification: black or coloured ⇒ Elec‐ tronic parts catalogue )

To ensure proper operation, gently screw the handwheel of the service coupling into the quick-release coupling adapter until the valve in the service connection opens reliably Monitor the pressure gauge closely and avoid overextending the valve.

♦ To remove and install the valve -3- with the refrigerant circuit drained, make use of an adapter from the socket -T10364- for example.

Various versions of these valves, featuring either internal or external threads, exhibit differing tightening torques Currently, the tightening torque for the -3- valves equipped with an M10 x 1.25 mm internal thread is 9 Nm ± 1 Nm.

Different versions of valves and their corresponding sealing caps exist, making it crucial to ensure the correct valve version is matched with the appropriate sealing cap for optimal performance.

Switches and senders in refrigerant circuit and related connections

Refer to vehicle-specific refrigerant circuit for switching pres‐ sures, switch removal/installation and switch layout/design ⇒

Heating, air conditioning; Rep gr 87 or ⇒ Air conditioning; Rep. gr 87 (vehicle-specific workshop manual).

♦ High-pressure switch for air conditioning system -F23-

♦ High-pressure switch for magnetic clutch -F118-

♦ Low-pressure switch for air conditioning system -F73-

♦ Air conditioning system pressure switch -F129- ⇒ page 30

♦ Refrigerant pressure and temperature sender -G395-

♦ Connections with valve for refrigerant circuit switches

♦ Air conditioner compressor regulating valve -N280-

♦ Air conditioning system compressor speed sender -G111-

2.5.1 High-pressure switch for air conditioning system -F23-

Switches the radiator fan up to the next speed setting in the event of a pressure increase in the refrigerant circuit (approx 16 bar).

2.5.2 High-pressure switch for magnetic clutch -F118-

Switches off the air conditioner compressor in the event of excess pressure in the refrigerant circuit (approx 32 bar).

2.5.3 Low-pressure switch for air conditioning system -F73-

Switches off the air conditioner compressor in the event of a pres‐ sure drop in the refrigerant circuit (approx 2 bar).

2.5.4 Connections with valve for refrigerant circuit switches

• There are different threads for switches on high and low-pres‐ sure sides.

• Only valves and O-rings resistant to R134a refrigerant and the related refrigerant oils are to be used.

To remove and install the valve core -C- with the refrigerant circuit drained, make use of an adapter from the socket -T10364- for example (tightening torque ⇒ page 26 ).

2.5.5 Air conditioning system pressure switch

This pressure switch has 3 functions:

1 Switches the radiator fan up to the next speed setting in the event of a pressure increase (approx 16 bar) in the refrigerant circuit.

2 Switches off the air conditioner in the event of excessive pres‐ sure (approx 32 bar) caused for example by inadequate engine cooling.

3 Switches off the air conditioner in the event of insufficient pres‐ sure (approx 2 bar) caused for example by a loss of refrigerant.

The air conditioning system pressure switch -F129- serves as a replacement for the high-pressure switch -F23-, the low-pressure switch -F73-, and the high-pressure switch for the magnetic clutch -F118-.

The high-pressure sender -G65- is fitted instead of the air condi‐ tioning system pressure switch -F129- or the refrigerant pressure and temperature sender -G395-

The refrigerant pressure and temperature sender -G395- (currently featuring a grey housing) and the high-pressure sender -G65- (now in a black housing) only differ in housing color; thus, it is crucial to ensure proper identification during replacement by consulting the electronic parts catalogue for the correct part number.

As these two senders emit different signals, the relevant control unit can only evaluate the signal to which it has been matched ⇒

The high-pressure sender -G65- generates a square-wave signal or data telegram when voltage is applied This signal changes with the pressure in the system.

The downstream control units, including the radiator fan control unit, engine control unit, and Climatronic air conditioning system components, utilize signals to assess refrigerant circuit pressure This information enables them to effectively manage the operation of radiator fans and the magnetic clutch of the air conditioning system, as well as adjust the air conditioner compressor regulating valve For detailed guidance, refer to the vehicle-specific workshop manual under Heating, Air Conditioning; Rep gr 87.

2.5.7 Refrigerant pressure and temperature sender -G395-

The refrigerant pressure and temperature sender -G395- is fitted instead of the high-pressure sender -G65-

The refrigerant pressure and temperature sender -G395- (currently with a grey housing) and the high-pressure sender -G65- (currently with a black housing) differ only in housing color It is crucial to ensure correct assignment during replacement, as indicated by the part number in the Electronic Parts Catalogue These senders produce different signals, and the relevant control unit can only interpret the signal it is matched with, as detailed in the Heating and Air Conditioning Repair Group 87 or the vehicle-specific workshop manual for Air Conditioning Repair Group 87.

When voltage is applied, the refrigerant pressure and temperature sender (G395) communicates with the control unit through the air conditioner data bus (Lin bus) This control unit utilizes the exchanged information to assess the refrigerant circuit's pressure and temperature, while also signaling any detected faults.

The refrigerant temperature recorded by the pressure and temperature sender -G395- varies due to its design and installation location, which leads to discrepancies with the actual refrigerant temperature in the circuit Consequently, this measurement is not currently utilized by all control units for air conditioning management.

The operating and display unit, Climatronic control unit -J255-, utilizes this information to calculate refrigerant circuit pressure and activate the subsequent control units.

The radiator fan control unit and engine control unit communicate via the data bus, allowing them to effectively manage the operation of radiator fans and the engine This coordination plays a crucial role in regulating heating and air conditioning systems in vehicles.

Rep gr 87 or ⇒ Air conditioning; Rep gr 87 (vehicle-specific workshop manual).

2.5.8 Air conditioner compressor regulating valve -N280-

The regulating valve is installed in the air conditioner compressor.

It is actuated by the operating and display unit for Climatronic air conditioning system -E87- or the Climatronic control unit -J255-

(possibly via the data bus and an additional control unit depending on the vehicle) ⇒ Heating, air conditioning; Rep gr 87 or ⇒ Air conditioning; Rep gr 87 (vehicle-specific workshop manual).

The pressure in the low-pressure side is influenced by way of the regulating valve, thus regulating the temperature in the evapora‐ tor.

The air conditioner compressor regulating valve -N280- is part of the air conditioner compressor and cannot be replaced separate‐ ly.

2.5.9 Air conditioning system compressor speed sender -G111-

The sender pulses, occurring four times per compressor revolution, along with the engine speed, allow the Climatronic air conditioning system's operating and display unit -E87- or the Climatronic control unit -J255- to accurately calculate belt slip.

If the belt slip exceeds a specified value, the air conditioner com‐ pressor is switched off by the control unit via the magnetic clutch.

♦ Fitted in Audi vehicles with compressor driven via poly V-belt and Zexel compressor ⇒ Heating, air conditioning; Rep gr

87 or ⇒ Air conditioning; Rep gr 87 (vehicle-specific work‐ shop manual).

♦ The logo of the compressor manufacturer „Zexel“ affixed to the air conditioner compressor was switched as of year of pro‐ duction 2006 (when the manufacturer's name changed) from

„Zexel“ to the new name „Valeo“.

The refrigerant temperature sender (with a temperature-sensitive resistor) is installed, for example, in the high-pressure pipe next to the air conditioner compressor.

In the refrigerant circuit, temperature and pressure are directly linked, meaning that a deficiency of refrigerant leads to a significant rise in temperature during air conditioner operation, exceeding expected levels for the given pressure.

♦ Fitted, for example, on the Audi Q7 with certain engines ⇒ Air conditioning; Rep gr 87 (vehicle-specific workshop manual) and ⇒ Current flow diagrams, Electrical fault finding and Fitting locations

The Climatronic control unit -J255- monitors the pressure and temperature in the refrigerant circuit, automatically shutting off the air conditioner compressor if the temperature exceeds the preset limit For detailed procedures, refer to the air conditioning section in the vehicle-specific workshop manual and utilize the vehicle diagnostic tester's self-diagnosis or guided fault-finding functions for troubleshooting.

Electrical components not installed in refrigerant circuit

♦ Radiator fan control unit -J293- ⇒ page 33

The control unit manages the activation and deactivation of the magnetic clutch, which in turn regulates the air conditioner compressor It also controls the radiator fans and monitors refrigerant pressure via the high-pressure sender -G65- For detailed information, consult the current flow diagrams, electrical fault finding, and fitting locations in the heating and air conditioning sections, specifically Rep gr 87.

Pressures and temperatures in refrigerant circuit

♦ When working on the refrigerant circuit, observe generally valid safety precautions and pressure vessel regulations.

The pressures and temperatures within the refrigerant circuit are influenced by real-time operating conditions, such as engine speed, radiator fan settings, engine temperature, and the status of the air conditioner compressor, alongside environmental factors like ambient temperature, humidity, and the necessary cooling output.

On vehicles with air conditioner compressor regulating valve -

N280- the pressure on the low pressure end is altered by actuat‐ ing -N280-

The values presented in the table serve as a general reference, achieved at engine speeds between 1500 and 2000 rpm and an ambient temperature of 20 °C after approximately 20 minutes of operation.

Refer to the vehicle-specific refrigerant circuit for the pressure gauge set measurement connections ⇒ Heating, air conditioning;

At 20 °C with the engine not running, the pressure in the refrig‐ erant circuit is 4.7 bar ⇒ page 3 (vapour pressure table).

Pressure can be measured in different units, where 1 MPa (megapascal) equals 10 bar gauge pressure or 145 psi Additionally, 1 bar of absolute pressure is equivalent to 0 bar gauge pressure, approximately matching atmospheric pressure.

♦ Refrigerant circuit with expansion valve ⇒ page 33

♦ Refrigerant circuit with restrictor and reservoir ⇒ page 35

2.7.1 Refrigerant circuit with expansion valve

HP – High-pressure side of refrigerant circuit

LP – Low-pressure side of refrigerant circuit

Component State of refrigerant Pressure (bar) Temperature in degrees centigrade -1- Evaporator, from inlet to outlet Vapour approx 1.2 bar 1) 1 approx -7 °C 2) 2

-2- Expansion valve Liquid, expanded to va‐ pour approx 14 bar approx +55 °C (high- pressure end), reduced to -7 °C (low-pressure end)

-3- High-pressure switch / high-pressure sender Liquid approx 14 bar approx +55 °C

-4- Service connection/ high-pressure end and-5- Receiver

-6- Condenser From gas (at inlet) via va‐ pour to liquid (at outlet) approx 14 bar From approx +65 °C (at inlet) to approx +55 °C (at outlet)

-7- Pressure relief valve and-8- Air conditioner com‐ pressor/high-pressure end

-9- Air conditioner com‐ pressor/low-pressure end Gas approx 1.2 bar 1) 1 approx -1 °C 2) 2

(not fitted on all vehicles) and-11- Service connection/ low-pressure end

The refrigerant circuit in a regulating air conditioner compressor maintains a pressure of approximately 2 bar absolute (or about 1 bar gauge) under varying heat transfer and engine speed conditions, but this stability is only effective within the compressor's output range; exceeding these limits will result in an increase in pressure.

The temperature in a refrigerant circuit of a regulated air conditioner compressor is kept stable within its designated range, even with changes in heat transfer and engine speeds This stability is effective only when operating within the compressor's output limits; exceeding these limits will result in a temperature rise.

♦ Non self-regulating air conditioner compressors are switched off by the relevant control unit via the air conditioner compres‐ sor regulating valve -N280- at evaporator temperatures below

♦ On vehicles with air conditioner compressor regulating valve -

N280- the pressure on the low pressure end is altered by actuating the valve.

In vehicles equipped with dual evaporators and expansion valves, the temperature and pressure within the refrigerant circuit mirror those found in models that utilize a single evaporator and expansion valve, indicating a parallel connection system.

♦ Depending on the design of the refrigerant circuit, a compo‐ nent with an internal heat exchanger may be fitted (e.g on the

The 2008 Audi A4 and Audi A5 Coupé feature a refrigerant pipe equipped with an internal heat exchanger This component allows the hot refrigerant in liquid form, moving through the high-pressure side, to transfer energy to the cold refrigerant in gaseous form on the low-pressure side, enhancing the vehicle's cooling efficiency.

3 - High-pressure switch / high- pressure sender

❑ Different versions de‐ pending on vehicle

4 - Service connection/high- pressure end

❑ Different versions de‐ pending on vehicle

8 - Air conditioner compressor/ high-pressure end

9 - Air conditioner compressor/ low-pressure end

❑ Not fitted on all vehicles

11 - Service connection/low- pressure end

2.7.2 Refrigerant circuit with restrictor and reservoir

Component State of refrigerant Pressure (bar) Temperature in degrees centigrade -1- Air conditioner com‐ pressor/high-pressure end

Gas Up to 20 bar Up to +70 °C

-2- Condenser From gas to vapour to liq‐ uid Up to 20 bar Up to +70 °C

The restrictor facilitates the transition from liquid to vapor at a high-pressure (HP) end of up to 20 bar and a low-pressure (LP) end exceeding 1.0 bar, with the HP end capable of reaching temperatures up to +60 °C and the LP end remaining above -4 °C Meanwhile, the evaporator converts vapor to gas at pressures greater than 1.0 bar and temperatures warmer than -4 °C.

Component State of refrigerant Pressure (bar) Temperature in degrees centigrade -6- Air conditioner com‐ pressor/low-pressure end Gas

The pressures on the low-pressure end are maintained at approx.

2 bar absolute (corresponding to approx 1 bar gauge) by the

The air conditioner compressor can be effectively regulated even when engine speeds fluctuate, but this regulation is only applicable within the compressor's designated output range For guidance on what to do if these output limits are surpassed, please refer to page 103.

On vehicles with air conditioner compressor regulating valve -

N280- the pressure on the low pressure end is altered by actuat‐ ing the valve.

1 - Air conditioner compressor/ high-pressure end

6 - Air conditioner compressor/ low-pressure end

Test and measurement operations which can be performed with a pressure gauge

which can be performed with a pressure gauge

1 - Temperature scale for refrigerant R134a CF3– CH2F or

Pressure can be measured in different units, with 1 MPa (megapascal) equating to 10 bar gauge pressure or 145 psi Additionally, 1 bar of absolute pressure is equal to 0 bar gauge pressure, which is approximately the same as atmospheric pressure.

Pressure gauges often include multiple temperature scales alongside the pressure scale The temperature scale values for R134a are determined based on the vapor pressure table Since various refrigerants exhibit distinct vapor pressures at identical temperatures, each temperature scale is specifically labeled for the corresponding refrigerant.

♦ Pressure gauges permit the following test and measurement operations ⇒ page 37

2.8.1 Pressure gauges permit the following test and measurement operations

Refrigerant circuit pressure and temperature measurements

The high-pressure gauge is essential for measuring the pressure and temperature that flow uniformly from the air conditioner compressor outlet through the condenser to the restrictor or expansion valve when the air conditioning system is activated.

The low-pressure gauge plays a crucial role in air conditioning systems by measuring the pressure and temperature that flow uniformly from the constriction point, such as a restrictor or expansion valve, through the evaporator to the compressor's inlet when the system is activated.

In a refrigerant circuit, the correlation between pressure and temperature is relevant only when liquid or vapor is present; this relationship does not apply to gas When in the gas state, the temperature can be approximately 10 °C to 30 °C higher than the reading on the pressure gauge.

Detection of refrigerant in a closed vessel

Refrigerant R134a is found within a closed vessel or refrigerant circuit, where the temperature displayed on the pressure gauge reflects the refrigerant's temperature, as the standing liquid equilibrates to the ambient temperature.

A closed vessel or a deactivated refrigerant circuit is empty if the temperature indicated on the pressure gauge is below the tem‐ perature of the refrigerant.

The relationship between pressure and temperature indicated on the pressure gauges no longer applies if no liquid is present and the pressure is built up solely by gas.

Air conditioner service and recycling units

Air conditioner service units for the extraction, cleaning and trans‐ fer of refrigerant for motor vehicle air conditioning systems are currently available from various manufacturers.

Only certain air conditioner service stations (with appropriate ad‐ ditional equipment and various adapters if applicable) can be used for flushing the refrigerant circuit ⇒ page 59

♦ Classification of extraction systems ⇒ page 38

♦ Charging systems that do not require a permit ⇒ page 38

Air conditioning service and recycling units in automotive workshops are classified as extraction and charging systems that do not require a permit (Group "3") However, these units should only be operated by qualified personnel to ensure safety and compliance For detailed guidance on operation and maintenance, refer to the manufacturer's documentation.

♦ Extraction and charging systems of groups „1“ and „2“ are not used in motor vehicle workshops.

Group „3“ extraction and charging systems:

Mobile extraction and charging systems for filling compressed- gas vessels permanently connected to the system

The refrigerant or refrigerant/oil mixture is transported to compressed-gas vessels that are permanently linked to mobile systems According to § 3 Para 5 No 3 of the German pressure vessel regulations, these compressed-gas vessels are categorized as pressure vessels, although different regulations may apply in other countries.

Compressed-gas vessels are classified as pressure vessels and do not necessitate expert testing for gas transfer However, a permit is essential for the system used to fill these compressed-gas vessels, and mandatory testing is required for transferring gas to other parties.

2.9.2 Charging systems that do not require a permit

Charging systems not requiring a permit are ones used for trans‐ ferring compressed gases to mobile compressed-gas vessels for internal use only.

Note: erant is not transferred to mobile compressed-gas vessels, but rather into a permanently installed charging cylinder with visible level gauge and float switch.

It is advisable to use a portable cylinder with visible level gauge and high-pressure safety valve for surplus refrigerant for internal use.

TRG 402 (technical regulations for compressed gases) must be observed when filling other compressed-gas vessels with com‐ pressed gases.

Repair notes for refrigerant circuit

♦ When working on the refrigerant circuit, observe generally valid safety precautions and pressure vessel regulations.

The performance of proper workmanlike repairs on an air condi‐ tioning system

• Requires the use of special tools and materials as listed on

• Requires compliance with the basic instructions for use of leak detectors ⇒ page 87

Releasing refrigerant into the environment is prohibited

The laws and regulations listed below are applicable in Germany.

Different or additional laws and regulations may apply in other countries.

Laws and regulations

Climate change is a pressing global issue, with its impacts evident worldwide Addressing climate protection is crucial, yet it poses significant challenges for everyone involved.

The Kyoto Protocol establishes global climate protection targets, setting specific reduction goals for both carbon dioxide and fluorinated greenhouse gases, such as the refrigerant R134a, due to its significant greenhouse gas potential.

Several important laws affecting the automobile industry have been enacted at the European level For instance, Germany implemented the climate protection regulation on chemicals on August 1, 2008, which provides more detailed guidelines in line with European legislation.

♦ Climate protection regulation on chemicals, recycling and re‐ fuse law (for Germany).

Maintenance and repair work on air conditioner refrigerant circuits

Proper maintenance and repair of motor vehicle air conditioning systems require individuals to have completed relevant training and possess certification of their qualifications It is important to note that additional regulations may apply in countries outside the European Community.

The following is however generally applicable:

Operation, maintenance, shutdown, obligation to accept return

It is essential to adhere to industry standards when operating, repairing, or shutting down equipment containing refrigerants, as releasing these substances into the atmosphere is strictly prohibited.

It is essential to maintain a record of quantities used during operations and maintenance to enable Audi-ServiceNet and HSO Environmental Protection to provide certification to authorities upon request As per a 2005 regulation by the European Parliament, keeping a record sheet is no longer mandatory within the European Community, although different regulations may apply in non-EC countries.

Distributors of the regulated substances and preparations are required to either take back these items after use or ensure their return through a designated third party.

Only individuals with the required expertise and technical equipment are authorized to maintain and shut down items containing regulated refrigerants, as well as to accept the return of substances and preparations specified in these regulations.

Criminal offences and infringements of the law

Any intentional or negligent action during the operation, maintenance, or shutdown of equipment containing specified refrigerants that results in the release of these substances into the atmosphere constitutes a violation of applicable regulations and laws This includes any failure to adhere to established best practices or legal requirements related to the handling of these materials.

TRG (technical regulations for compressed gases) 400, 401, 402

Only excerpts from the TRG are given in the following (sections applicable to motor vehicle manufacturers and workshops).

♦ TRG 400 (general regulations for charging systems)

– Definition of terms and explanatory notes

– Charging systems are systems for filling mobile compressed- gas vessels The charging system includes the premises and facilities concerned.

♦ Charging systems requiring a permit are ones used to transfer compressed gases to mobile compressed-gas vessels for supplying to third parties.

♦ Charging systems not requiring a permit are ones used for transferring compressed gases to mobile compressed-gas vessels for internal use only.

♦ TRG 401 (installation of charging systems)

– Does not apply to vehicle manufacturers or workshops.

♦ TRG 402 (operation of charging systems)

– Employees and the instruction of employees

Employees are to be given instruction on the following topics be‐ fore beginning work and at regular, appropriate intervals, however at least once a year:

• Hazards specifically associated with handling compressed gases

• Safety regulations, particularly the applicable TRG

• Procedures in the event of malfunction, damage and accidents

• The use of fire-extinguishing and protective equipment

• Operation and maintenance of the charging system on the ba‐ sis of the instructions for use

– Charging systems may only be operated and maintained by persons:

– Possessing the necessary technical knowledge.

– Who can be relied upon to work diligently.

Work under supervision may also be performed by persons who fail to comply with the above-mentioned prerequisites.

Charging (a special TRG applies to vessels from other countries and charging of these).

A compressed-gas vessel must only be filled with the specific compressed gas indicated on its label, and the amount filled must adhere to the specified pressure, weight, or volume limits as outlined in pressure vessel regulations.

Vessels approved for multiple types of compressed gas must clearly indicate the specific gas intended for filling, along with the maximum permissible charging weight in accordance with TRG 104, particularly when the critical temperature (tc) of the gas is equal to or greater than -10 °C.

Compressed-gas vessels should be filled manometrically, adhering to the maximum permissible charge pressure indicated in bar at 15 °C If the filling occurs at a different temperature, the pressure must be adjusted according to the current temperature to ensure that the permissible charge pressure at 15 °C is not surpassed Additionally, random pressure measurements should be conducted on the filled vessels to check for potential overfilling.

♦ Compressed-gas vessels on which the maximum permissible capacity is indicated by the net weight (filling weight, permis‐ sible weight of fill) in kilograms must be filled gravimetrically.

During the filling process, vessels should be weighed and then checked for weight on calibrated scales to identify any potential overfilling.

Gases with a critical temperature (tc) of 70 °C or higher can be volumetrically transferred from compressed-gas vessels of up to 150 liters to those with a maximum volume of 1000 ccm, provided certain conditions are met It is essential to adhere to the regulations outlined in the TRG when transferring liquefied gas to cylinders utilized by workers.

♦ The following TRG apply to vessels in vehicles:

– TRG 101 to gases with a tc ≥ +70 °C.

– TRG 102 or TRG 103 to industrial gas mixtures with a tc ≥

Liquefied extremely low-temperature compressed gases can be filled volumetrically, except for vessels in vehicles, provided that the charging system and vessels are equipped with devices to measure or limit the charge volume and temperature It is essential to ensure that the vessel's capacity is not exceeded during the filling process To prevent overfilling, charged vessels should be verified using calibrated scales or volumetric methods, as long as the compressed gases are not highly toxic Proper volumetric checks necessitate the use of specialized equipment with distinct charging and checking devices.

♦ Charging and check measurements must be performed by different people Check measurements must be performed immediately upon completion of the filling process.

♦ Overfilled vessels must be discharged immediately and safely until the permissible filling quantity is reached The com‐ pressed-gas fill must then be determined again.

Important repair notes for air conditioning systems

• Air conditioners for refrigerant R12 may only be filled with re‐ frigerant R134a if certain prerequisites are satisfied

⇒ page 44 and ⇒ Workshop Manual: Air conditioner with re‐ frigerant R12 Part 2 and 3 This Workshop Manual is only available in hardcopy form.

• The refrigerant oils specifically developed for R134a and R12 refrigerant circuits are never to be mixed.

• Air conditioner service stations which come into contact with the refrigerant should only be used for the intended refrigerant.

• The components of an R134a refrigerant circuit are accord‐ ingly labelled, marked with green stickers or designed (e.g a different thread) such that interchange with components for refrigerant R12 is not possible.

• The refrigerant being used is indicated by a label affixed to the lock carrier in the engine compartment or in the plenum cham‐ ber.

When working on the refrigerant circuit, always pay attention the information given in the Sections on „Safety measures“

⇒ page 13 and „Basic rules for working on refrigerant circuit“

Converting refrigerant circuits from refrigerant R12 to refrigerant R134a

CFC refrigerants are no longer used in the automotive industry.

For conversion of refrigerant circuits from R12 to R134a and servicing converted circuits, refer to

⇒ Workshop Manual: Air conditioner with refrigerant R12 Parts 2 and 3 (this Workshop Manual is only available in printed form).

Working with the air conditioner service station

If there is a chance that sealing additives have been introduced into the refrigerant circuit, refrain from connecting the air conditioner service station or extracting the refrigerant from that circuit.

Chemical sealing additives used to seal leaks in refrigerant circuits can create deposits that negatively affect the performance of air conditioning systems, potentially leading to system failures and issues at air conditioner service stations.

Customers need to be aware that the air conditioning system in their vehicle contains substances that are not approved by Audi As a result, servicing and discharging the system cannot be performed by your workshop.

♦ Audi does not permit the use of chemical substances (sealing additives) to seal leaks in the refrigerant circuit.

Chemical sealing additives used for leaks in refrigerant circuits often react with ambient air and humidity, leading to deposits that can cause malfunctions in valves and other components These deposits are difficult to eliminate completely, affecting both the refrigerant circuit and the air conditioner service station.

Chemical sealing additives used to fix leaks in refrigerant circuits are often not visibly detectable, and the necessary identification stickers are frequently missing As a result, vehicles with an uncertain maintenance history should be approached with caution.

The accessories market offers vessels equipped with integrated filters designed to capture chemical substances, specifically additives used for sealing leaks However, Audi opposes the use of these substances, leaving the effectiveness and interception rate of these filters unverified.

♦ Important notes for working with the air conditioner service station ⇒ page 47

♦ Connection of the air conditioner service station for measure‐ ment and testing ⇒ page 47

♦ Refrigerant circuit discharge using the air conditioner service station ⇒ page 48

♦ Refrigerant circuit evacuation using the air conditioner service station ⇒ page 49

♦ Refrigerant circuit charging using the air conditioner service station ⇒ page 53

♦ Air conditioner start-up after charging ⇒ page 53

♦ Pouring refrigerant into the charging cylinder or storage vessel of the air conditioner service station ⇒ page 54

♦ Air conditioner service station drainage ⇒ page 55

4.3.1 Important notes for working with the air conditioner service station

The following must be heeded with regard to operation of air con‐ ditioner service stations (e.g V.A.G 1885; for currently available air conditioner service stations, refer to ⇒ V.A.G workshop equip‐ ment catalogue ):

– The filters and dryers fitted must be replaced at the latest at the end of the period of use specified in the corresponding operating instructions.

– If an air conditioner service station is also used to flush the refrigerant circuit, the dryers and filters fitted must be renewed more frequently ⇒ page 55

Only refrigerant oils that are approved for the specific refrigerant circuit of the vehicle should be used If applicable, add the refrigerant oil directly to the refrigerant circuit, as indicated in the electronic parts catalogue.

When there is uncertainty regarding the composition of the refrigerant extracted from the refrigerant circuit, it should not be reused, even after undergoing cleaning at the air conditioner service station.

– In such cases, the air conditioner service station is to be drained ⇒ page 99 , the system cleaned if necessary and the filters, dryers and refrigerant oil replaced.

In Germany, contaminated refrigerants can be returned to suppliers using designated recycling bottles for proper recycling or ecological disposal, although different regulations may apply in other countries.

Commercially available air conditioner service stations can be classified in 2 groups:

Air conditioner service stations, such as V.A.G 1885, specialize in cleaning and recycling refrigerant extracted from vehicles For a comprehensive list of currently available air conditioner service stations, please refer to the V.A.G workshop equipment catalogue.

♦ Air conditioner service stations which transfer extracted re‐ frigerant to recycling containers (for large-scale recycling); these are referred to as extraction systems.

4.3.2 Connecting air conditioner service sta‐ tion for measuring and testing

• Work procedure may vary depending on the type of tools se‐ lected; therefore it is important to observe the tool-specific operating instructions.

The work procedure must always be performed as described in the operating instructions of the air conditioner service station.

To prevent air or moisture entering the refrigerant circuit through the charging hoses, these are to be connected as follows:

– Connect air conditioner service station to power supply.

To begin the procedure, remove the sealing caps from the service connections or valve connections, following the guidelines outlined in the vehicle-specific refrigerant circuit For detailed instructions, consult the heating and air conditioning section, specifically Repair Group 87, in the vehicle-specific workshop manual.

– Evacuate the charging hoses if necessary.

– Connect quick-release coupling to service connection of re‐ frigerant circuit.

Avoid opening the valves on either the low or high-pressure sides while the engine is running, as this can lead to a short circuit in the refrigerant circuit This could potentially damage the air conditioner compressor or the service station if the air conditioning system is operational.

To ensure safe operation, only tighten the handwheel on the quick-release coupling adapter enough to effectively open the valve in the service connection, while monitoring the pressure gauge to avoid overextending the valve.

– Start the engine and perform the intended tests and meas‐ urements.

– Compare the values determined to the specified measured values ⇒ page 103

– Before detaching quick-release coupling, close it by screwing out handwheel.

Vehicles with one service connection only:

To connect the refrigerant circuit, attach the valve adapters -V.A.G 1785/9-, -V.A.G 1785/10-, or the adapter set -V.A.G 1786- to the designated connections Ensure to bleed the charging hoses while connecting to the adapters, allowing only a faintly audible escape of refrigerant gas For detailed instructions, refer to page 99.

– The charging hose must be fitted with a valve opener to open the valve in the valve adapter.

4.3.3 Discharging refrigerant circuit with air conditioner service station

• Work procedure may vary depending on the type of tools se‐ lected; it is therefore important to observe the tool-specific operating instructions.

Before removing any components from the refrigerant circuit, it is essential to discharge the system This step is crucial if there is uncertainty regarding the amount of refrigerant present or if safety measures dictate its necessity.

• All the necessary usage information for working with the re‐ frigerant air conditioner service station can be found in the air conditioner service station operating instructions.

Blowing out refrigerant circuit with compressed air and nitrogen

To effectively remove moisture, impurities, and old refrigerant oil from the refrigerant circuit while minimizing refrigerant loss and extensive assembly work, it is recommended to flush the circuit with refrigerant R134a or use compressed air and nitrogen This method also ensures environmental compatibility.

Flushing the refrigerant circuit with R134a is more effective and efficient than using compressed air and nitrogen, as it ensures superior cleaning of the components Therefore, flushing should be the preferred method when addressing complaints, while blowing out the circuit should be reserved for specific issues and components.

In specific situations, using compressed air and nitrogen to blow out particular components, such as refrigerant pipes or hoses, can effectively remove old refrigerant oil after the components have been detached.

♦ Certain impurities are impossible or difficult to remove properly from the refrigerant circuit using compressed air Such impur‐ ities can be removed for example by flushing with refrigerant

When performing blowout procedures, it is essential not to exceed a maximum working pressure of 15 bar, which aligns with the pressure found in a charged refrigerant circuit at approximately 60 °C Additionally, if applicable, a pressure reducer should be used for compressed air to ensure safety and compliance.

♦ Always work with pressure reducers for nitrogen cylinders

♦ Use appropriate extraction units to draw off gas mixture escaping from components.

– Always flush or blow out components in direction opposite to refrigerant flow.

The restrictor, expansion valve, air conditioner compressor, re‐ ceiver and reservoir cannot be flushed with compressed air and nitrogen.

– In the case of condensers fitted with a dryer cartridge in the integrated receiver, this cartridge is to be removed.

♦ In the case of condensers with an integrated receiver / dryer cartridge which cannot be renewed separately, the condenser is to be replaced after flushing.

Depending on the model, some receivers allow for separate replacement of the dryer cartridge, and these may include an additional filter element that should be replaced simultaneously with the dryer cartridge.

– First flush out the old refrigerant oil and dirt with compressed air and then use nitrogen to remove the moisture from the components.

– For adapter for connecting pressure hose to refrigerant circuit, refer to ⇒ page 99

Observe the following to prevent oil and moisture from the com‐ pressed-air system from ingressing into the refrigerant circuit.

To ensure optimal performance in painting work, it is essential to clean and dry compressed air using a compressed-air purifier This process involves utilizing filters and dryers specifically designed for compressed air, which are included in the workshop equipment and special tools catalogue.

– For refrigerant pipes with a thread or union nut at the connec‐ tion, make use of adapters from the adapter set for refrigerant circuit -V.A.G 1785- ( adapter -V.A.G 1785/1- to adapter -

V.A.G 1785/8- ) for connection of the 5/8" -18 UNF charging hoses (some of these adapters are also contained in the VW/

Audi passenger vehicle adapter set -VAS 6338/1- ).

– For refrigerant pipes with no thread or union nut at connection

(for connecting adapters), use adapters from adapter set for refrigerant circuits -VAS 6338/1- or commercially available blow-out gun with rubber mouthpiece.

If flushing the refrigerant circuit is not feasible or if it requires excessive effort, using compressed air followed by nitrogen to blow out the circuit is acceptable This method effectively removes minor impurities and small amounts of moisture from refrigerant pipes without consuming much time.

♦ Compressed air/nitrogen emerging from the components is to be drawn off by way of an appropriate system (e.g workshop extraction system).

The refrigerant circuit (or individual components) is/are to be blown out if no means of flushing are available or if flushing seems inappropriate

– In the event of dirt or other impurities in individual circuit com‐ ponents

– If the vacuum reading is not maintained on evacuating a leak- free refrigerant circuit (pressure build-up due to moisture in refrigerant circuit)

– If the refrigerant circuit has been left open for longer than the normal assembly time (e.g following an accident)

– If pressure and temperature measurements in the refrigerant circuit indicate the likelihood of moisture

– If there are doubts about the amount of refrigerant oil in the refrigerant circuit

– If the air conditioner compressor has to be replaced on ac‐ count of internal damage (e.g noise or no output)

– If stipulated by the vehicle-specific Workshop Manual after re‐ newing certain components

Removing certain impurities and old refrigerant oil from the refrigerant circuit using compressed air can be challenging A more effective method for eliminating these contaminants is to flush the system with refrigerant R134a.

♦ Blowing out refrigerant circuit ⇒ page 58

For vehicles lacking threaded refrigerant lines for V.A.G -1785- adapter connections, utilize a blow-out gun with a rubber mouthpiece or an adapter from the VW/Audi passenger vehicle adapter set -VAS 6338/1- to effectively blow out individual components.

Special care must be taken not to damage the connections

(crushing or scratching) when using a blow-out gun with rub‐ ber mouthpiece.

♦ The evaporator is to be blown out by way of the connection for the low-pressure pipe (large diameter) after detaching the ex‐ pansion valve or removing the restrictor.

♦ Always flush or blow out components in direction opposite to refrigerant flow.

♦ Check expansion valve and renew if dirty or corroded.

♦ If dark, sticky deposits cannot be removed with compressed air, flush the components concerned with refrigerant R134a or renew.

♦ Thin, light grey deposits on the insides of pipes do not impair the function of the components.

♦ After flushing, always renew receiver or reservoir and restric‐ tor In the case of condensers fitted with a dryer cartridge in the integrated receiver, this cartridge is to be replaced.

If a condenser features an integrated receiver/dryer cartridge that cannot be separately replaced or is unavailable as a replacement part, it is necessary to replace the entire condenser after flushing Please refer to the electronic parts catalogue for further details.

Heating, air conditioning; Rep gr 87 or ⇒ Air conditioning;

Depending on the model, some receivers allow for the separate replacement of the dryer cartridge, and these may also include an additional filter element that needs to be replaced along with the cartridge.

After blowing out the refrigerant circuit:

– Replace the vehicle-specific components (restrictor and res‐ ervoir, expansion valve and receiver or dryer cartridge) ⇒

Rep gr 87 (vehicle-specific workshop manual) and ⇒ Elec‐ tronic parts catalogue

To address specific issues with your air conditioning system, it may be necessary to replace the air conditioner compressor Refer to the vehicle-specific workshop manual for guidance on heating and air conditioning repairs, particularly Rep gr 87 Additionally, consult the electronic parts catalogue for detailed components Ensure to drain any remaining refrigerant oil from the removed air conditioner compressor before proceeding with the installation of the new unit.

⇒ page 136 (replace refrigerant circuit components) and add the specified quantity of fresh refrigerant oil again

⇒ page 164 (approved refrigerant oils and refrigerant oil ca‐ pacities).

Replacement compressors come with a specific amount of refrigerant oil In vehicles equipped with two evaporators, it may be necessary to supplement the system with additional refrigerant oil to ensure optimal performance.

Air conditioning; Rep gr 87 (vehicle-specific workshop man‐ ual) and ⇒ page 164 (approved refrigerant oils and refrigerant oil capacities).

To maintain optimal performance of the air conditioner compressor without replacement, it is essential to top up the refrigerant oil to the specified capacity This involves draining the existing refrigerant oil and adding the correct amount to the compressor or refrigerant circuit, as detailed on page 136 for replacing refrigerant circuit components and page 164 for approved refrigerant oils and their capacities.

– Completely re-assemble the refrigerant circuit ⇒ Heating, air conditioning; Rep gr 87 or ⇒ Air conditioning; Rep gr 87

– Evacuate and charge the refrigerant circuit as specified

– Start up the air conditioner as specified ⇒ Heating, air condi‐ tioning; Rep gr 87 or ⇒ Air conditioning; Rep gr 87 (vehicle- specific workshop manual) and ⇒ page 53

Flushing (cleaning) refrigerant circuit with refrigerant R134a

If there is a chance that sealing additives have been introduced into the refrigerant circuit, avoid connecting the air conditioner service station to this circuit and refrain from flushing it.

Chemical sealing additives used to seal leaks can create deposits within the refrigerant circuit, negatively impacting the performance of the air conditioning system and potentially leading to system failure and issues at the air conditioner service station.

Customers must be made aware that their vehicle's air conditioning system contains substances not authorized by Audi, which means it cannot be flushed or serviced at your workshop.

♦ Audi does not permit the use of chemical substances (sealing additives) to seal leaks in the refrigerant circuit.

Chemical sealing additives used to fix leaks in refrigerant circuits often react with ambient air and humidity, leading to the malfunction of valves and other components This reaction results in deposits within the refrigerant circuit and at the air conditioner service station, which cannot be entirely eliminated from the affected components.

(even by flushing) The refrigerant circuit can therefore only be repaired by replacing all the components which have come into contact with this substance.

Chemical sealing additives used to fix leaks in refrigerant circuits often go unnoticed, and the identification stickers meant to indicate their presence are frequently missing As a result, it's essential to exercise caution when dealing with vehicles that have an unclear maintenance history.

To effectively remove moisture, impurities, and old refrigerant oil from the refrigerant circuit without significant refrigerant loss or extensive assembly work, it is recommended to flush the system using refrigerant R134a This method ensures environmental compatibility while maintaining system efficiency.

The refrigerant circuit is to be flushed:

– In there is any dirt or similar in the circuit.

– If the vacuum reading is not maintained on evacuating a leak- free refrigerant circuit (pressure build-up due to moisture in refrigerant circuit)

– If the refrigerant circuit has been left open for longer than the normal assembly time (e.g following an accident)

– If pressure and temperature measurements in the refrigerant circuit indicate the likelihood of moisture

– If there are doubts about the amount of refrigerant oil in the refrigerant circuit

– If the air conditioner compressor has to be replaced on ac‐ count of internal damage (e.g noise or no output)

– If stipulated by the vehicle-specific Workshop Manual after re‐ newing certain components

♦ Air conditioner service station with flushing attachment (these air conditioner service stations feature the additional function

„Flushing refrigerant circuit“ and the necessary flushing at‐ tachment for refrigerant circuits) ⇒ Workshop equipment and special tools catalogue

♦ Adapter set for refrigerant circuits -VAS 6338/1- ⇒ page 71 and ⇒ Workshop equipment and special tools catalogue

If an air conditioner service station with a flushing attachment is unavailable, consult the workshop equipment and special tools catalog Depending on the specific version of the air conditioner service station, the refrigerant circuit can be flushed using the appropriate refrigerant circuit flushing attachment.

⇒ Workshop equipment and special tools catalogue , however flushing must then be performed manually ⇒ page 65

♦ Use can be made for vehicles with screw connections at the refrigerant circuit of the adapter -V.A.G 1785/7- and adapter -

V.A.G 1785/8- from the VW/Audi passenger vehicle adapter set -VAS 6338/1- Two adapters -V.A.G 1785/8- are required for a vehicle with screw connections at the air conditioner compressor and reservoir.

♦ The adapter set for refrigerant circuits -VAS 6338/1- also con‐ tains a short filler hose -VAS 6338/31- with 5/8 -18 UNF connections and a large inside diameter (commercially avail‐ able).

– Discharge the refrigerant circuit ⇒ page 48

– Remove the air conditioner compressor ⇒ Heating, air condi‐ tioning; Rep gr 87 or ⇒ Air conditioning; Rep gr 87 (vehicle- specific workshop manual).

Vehicle with restrictor and reservoir

– Remove restrictor (vehicle-specific) and re-connect pipes ⇒

Rep gr 87 (vehicle-specific Workshop Manual).

To remove the vehicle-specific reservoir, reconnect the pipes using an adapter and the charging hose (VAS 6338/31) from the VW/Audi passenger vehicle adapter set (VAS 6338/1) Refer to page 71 under Heating, Air Conditioning; Rep Gr 87 or Air Conditioning; Rep Gr 87 for detailed instructions.

Flushing the reservoir is feasible, but its large internal volume retains an excessive amount of liquid refrigerant When this refrigerant is extracted, the reservoir risks severe icing, leading to a slow evaporation process and an extended extraction duration.

Vehicle with expansion valve and receiver

To disconnect the receiver, which is vehicle-specific and may not be required for all vehicles, use an adapter along with the charging hose (VAS 6338/31) to reconnect the pipes.

VW/Audi passenger vehicle adapter set -VAS 6338/1- )

⇒ page 71 , ⇒ Heating, air conditioning; Rep gr 87 or ⇒

Air conditioning; Rep gr 87 (vehicle-specific workshop man‐ ual).

♦ Depending on design, the receiver can be flushed (remove the fitted dryer cartridge if applicable) ⇒ page 71 , ⇒ Heating, air conditioning; Rep gr 87 or ⇒ Air conditioning; Rep gr

For Audi A3 models from 2004 onward, the receiver attached to the condenser does not need to be removed for flushing, as its design allows for effective flushing It is only necessary to replace the receiver after the flushing process is completed For detailed instructions, refer to page 71 or consult the vehicle-specific workshop manual under Heating, Air Conditioning; Rep gr 87 or Air Conditioning; Rep gr 87.

When dealing with condensers that feature an integrated receiver/dryer cartridge that cannot be replaced independently, it is necessary to replace the entire condenser after flushing For these vehicles, the condenser should be replaced in conjunction with the receiver to ensure optimal heating and air conditioning performance.

Rep gr 87 and ⇒ Electronic parts catalogue

Depending on the model, some receivers allow for the separate replacement of the dryer cartridge, which may come with an additional filter element that also needs to be replaced alongside the cartridge.

– On vehicles with a dryer cartridge in the receiver at the con‐ denser (vehicle-specific), remove the dryer cartridge and reseal the opening at the receiver ⇒ Heating, air conditioning;

– Remove the expansion valve (vehicle-specific) and replace it with an adapter from the VW/Audi passenger vehicle adapter set -VAS 6338/1- ⇒ page 71 , ⇒ Heating, air conditioning;

♦ If there is no suitable adapter for the expansion valve in the

The VW/Audi passenger vehicle adapter set, designated as VAS 6338/1, allows for the removal and drilling of the old expansion valve, which typically needs replacement and is thus rendered unnecessary.

♦ Before drilling open, remove the control element and then drill open the expansion valve using a suitable drill bit for example

Different versions of expansion valves feature varying designs For version -A-, components -B-, -C-, and -D- must be removed Next, detach part -E- (the control element) from part -D- After completing these steps, use an appropriate drill bit to open the expansion valve in area -F-.

♦ With version -G-, the parts -H-, -I- and -K- must be removed for example and the area -L- then drilled open using a suitable bit.

– Remove swarf remnants from the expansion valve after drilling open.

– Re-install the parts -B-, -C- and -D- with version -A- or part

Tracing leaks in refrigerant circuit

♦ Minor leaks can be detected with an electronic leak detector or UV leak detector lamp for example.

This Workshop Manual outlines two effective methods for detecting leaks in refrigerant circuits When executed properly and in alignment with the specific issue at hand, these tested procedures yield reliable results across various usage conditions.

There are various systems on the market designed for detecting refrigerant circuit leaks, but not all provide reliable results Improper use of these systems may falsely indicate leaks in intact components Furthermore, certain procedures can potentially damage refrigerant circuit components.

♦ Components found to be leaking are to be replaced and not repaired.

♦ Leaking refrigerant circuits are not to be filled with refrigerant.

Empty refrigerant circuits are therefore to be evacuated before filling with refrigerant and checked for leaks in this process

♦ Audi does not permit the use of chemical substances

(sealing additives) to seal leaks in the refrigerant circuit.

Chemical leak sealing substances can create deposits in the refrigerant circuit, negatively affecting the air conditioning system's performance and potentially causing system failure, which also impacts the air conditioner service station.

Chemical sealing additives used for leaks in refrigerant circuits can react with ambient air or humidity, leading to malfunctions in valves and other components due to deposits formed in the circuit and service station These deposits are not fully removable, even with flushing, necessitating the replacement of all components that have been in contact with the sealing substance for effective repair.

♦ ⇒ „4.6.1 Tracing refrigerant circuit leaks with electronic leak detector (e.g V.A.G 1796)“, page 88

♦ ⇒ „4.6.2 Tracing leaks in refrigerant circuit with leak detection system VAS 6201“, page 89

4.6.1 Tracing refrigerant circuit leaks with electronic leak detector (e.g V.A.G

Proceed as follows with a completely empty refrigerant circuit to avoid allowing more refrigerant than is absolutely necessary for leak detection to escape into the environment:

– Evacuate the refrigerant circuit using the air conditioner serv‐ ice station ⇒ page 49

♦ If evacuation already reveals a major leak, this is to be located and eliminated as described ⇒ page 49

♦ Continue as follows if evacuation does not reveal any leakage or if the leakage is so slight that it is not possible to determine the leakage location.

– Pour roughly 100 g of refrigerant into the evacuated refrigerant circuit.

– Start up leak detector in line with relevant operating instruc‐ tions.

– Always hold test probe beneath suspected leak.

Depending on the model, leak detection is indicated by an in‐ crease in clicking rate or a warning tone (refer to operating in‐ structions for leak detector).

♦ Currents of air quickly disperse refrigerant gas Draughts must therefore be avoided during leak detection.

♦ Refrigerant gas is heavier than air and therefore sinks to a lower level at the exit location.

4.6.2 Tracing leaks in refrigerant circuit with leak detection system VAS 6201

♦ Certain leaks are difficult or even impossible to find using an electronic leak detector In such cases, the leak detection sys‐ tem VAS 6201 can be used.

Refrigerant circuit leaks lead to the escape of both refrigerant and refrigerant oil, which typically accumulates near the leak site By introducing a small amount of fluorescent fluid into the refrigerant circuit, the oil becomes visible under UV light, aiding in leak detection.

UV light is utilized in air conditioning systems by introducing a fluid, specifically PAG oil with a UV-reactive additive, into the refrigerant circuit When the air conditioner is activated, this fluid disperses throughout the refrigerant oil, enhancing the system's efficiency and facilitating leak detection.

To ensure effective distribution of the additive throughout the refrigerant circuit, the air conditioner should be operated for a minimum of 60 minutes, allowing the compressor to run continuously Depending on the severity of the leak, the location of the leak may become visible under UV light during this time.

The refrigerant oil, infused with a UV-reactive additive, can be introduced into the open circuit either by direct pouring or by using a hand pump to inject it while the circuit is charged.

VAS 6201/1 (from the leak detection system VAS 6201) via the service connection on the low-pressure end.

When applying leak detection additive through the service connection on the low-pressure side of a charged refrigerant circuit, it is crucial to ensure that any residual additive in the service connection is properly removed to prevent inaccurate leak detection results.

When renewing a component in a refrigerant circuit that has been treated with a leak detection additive, it is essential to thoroughly clean the joints with other components after assembly Failure to do so may lead to residual additive at the joints being misidentified as a leak during future leak detection efforts.

When discharging the refrigerant circuit, refrigerant oil and leak detection additives enter the air conditioner service station The oil is separated from the refrigerant in the station's oil separator and is drained away It is crucial not to reuse the drained refrigerant oil; instead, it should be replaced with fresh refrigerant oil to ensure optimal air conditioner performance.

When adding leak detection fluid to a refrigerant circuit after previous repairs, ensure that fresh fluid is only introduced if the refrigerant oil has been fully replaced If only a portion of the refrigerant oil is changed, add an equivalent amount of leak detection fluid For instance, if 100 ml of refrigerant oil is replaced in a system that originally contained 250 ml, then only 1 ml of leak detection additive should be added.

♦ Certain materials and their compounds (e.g oxidation prod‐ ucts on aluminium components, anti-corrosion waxes) also show up under UV light.

To effectively detect refrigerant circuit leaks while minimizing environmental impact, ensure that the refrigerant circuit is completely empty before beginning the process This approach prevents excessive refrigerant from escaping into the atmosphere during leak localization.

– Evacuate the refrigerant circuit using the air conditioner serv‐ ice station ⇒ page 49

♦ If evacuation already reveals a major leak, this is to be located and eliminated as described ⇒ page 49

♦ Continue as follows if evacuation does not reveal any leakage or if the leakage is so slight that it is not possible to determine the leakage location.

For leakage which cannot be determined by way of evacuation, refer to ⇒ page 90

Tools and other items required:

1 - Hand pump with low-pressure service hose, service cou‐ pling and non-return valve -VAS 6201/1-

4 - UV leak detection lamp -VAS 6201/4-

5 - UV-absorbing eye protection -VAS 6201/6-

Pouring in leak detection additive with refrigerant circuit empty

The cartridge -A- contains 15.4 ml of leak detection additive (one unit -B- corresponds to 2.5 ml).

– Assemble hand pump -VAS 6201- , item -1- with cartridge, item -2- -VAS 6201/2-

– Insert filler tube -VAS 6201/8- ( ⇒ page 90 item -7-) in hand pump.

– Open hand pump service valve.

♦ When the refrigerant circuit is empty, the leak detection addi‐ tive can be poured into the circuit via a service connection or an open connection.

When the refrigerant circuit is empty, it's advisable to apply a leak detection additive through a joint, especially if it has already been loosened This method ensures that no additive remains in the service connection, eliminating the need for cleaning the connection afterward.

♦ Application of leak detection additive to the refrigerant circuit by way of a service connection ⇒ page 93

♦ Application of leak detection additive to the refrigerant circuit by way of an open connection ⇒ page 92

Applying leak detection additive to the refrigerant circuit by way of an open connection

– Open the refrigerant circuit at a readily accessible connection.

– Cover the surrounding area with sheeting or absorbent paper.

– Screw in the toggle of the hand pump until the leak detection additive emerges from the tube.

– Fill the refrigerant circuit with 2.5 + /- 0.5 ml (millilitre = cm 3 ) of leak detection additive.

If leak detection fluid has previously been added to a refrigerant circuit during repairs, it is essential to only introduce fresh leak detection fluid when the refrigerant oil is replaced.

Possible complaints about refrigerant circuit

• Electrical system, vacuum system and air duct fault-finding has not revealed any faults ⇒ Vehicle diagnostic tester ( „self- diagnosis“ or „guided fault-finding“ function for air conditioner),

⇒ Current flow diagrams, Electrical fault finding and Fitting lo‐ cations and ⇒ Heating, air conditioning or ⇒ Air conditioning

• Air conditioner self-diagnosis/guided fault-finding with the ⇒

Vehicle diagnostic tester has not revealed any faults, no com‐ pressor shut-off criteria displayed in measured value block

(vehicles with „air conditioner“ self-diagnosis only) ⇒ Heating, air conditioning or ⇒ Air conditioning or „Guided fault-finding“ function ⇒ Vehicle diagnostic tester

♦ For all complaints marked *, refer to ⇒ page 103 „Checking pressures“.

♦ If problems are only encountered at one evaporator on vehi‐ cles fitted with two evaporators, also check the pressures in the refrigerant circuit.

♦ Heed the test conditions ⇒ page 97

♦ Insufficient cooling output at all vehicle or engine speeds.*

♦ No cooling or insufficient cooling after driving a few miles *

♦ No or insufficient cooling at one or via both evaporators (on vehicles with two air conditioner units) *

♦ Air conditioner compressor, air conditioning system magnetic clutch -N25- or air conditioner compressor regulating valve -

N280- shut off by a pressure switch (e.g -F73-, -F118-, -F129-

-F129- or by the operating and display unit for Climatronic air conditioning system -E87- or the Climatronic control unit -

J255- ) on account of excessive or inadequate pressure *

♦ No or sharp decrease in fresh-air supply after driving several miles (evaporator iced up) *

– Re-tighten the bolts for the air conditioner compressor and the compressor holder using a torque wrench.

– Check routing of refrigerant pipes; they must not touch other components and must not be subject to strain (align if neces‐ sary).

Noise (refrigerant hammer) occurring immediately after switching on the air conditioner and/or when cornering or braking

– Discharge, evacuate and re-charge refrigerant circuit (too much refrigerant in circuit).

Too much refrigerant oil in the circuit may also result in this prob‐ lem (no adjustment of refrigerant oil quantity, for example, on replacing compressor).

Water sprays out of the vents (in the dash panel or footwell) al‐ though the air conditioning system is otherwise functioning prop‐ erly

– Check proper routing of condensate drain; it must not be crushed or kinked.

– Check the condensate drain valve; it must not be gummed up with wax or underseal and must close properly.

– Check the plenum chamber cover; it must not be damaged and must be properly installed (to stop water running into the evaporator).

– Check the plenum chamber water drains; they must not be blocked (e.g by leaves).

6 Connecting air conditioner service station

♦ Air conditioner service station connection on vehicles with a connection on the low and high-pressure end of the refrigerant circuit ⇒ page 99

♦ Air conditioner service station connection on vehicles with no connection on the low-pressure end of the refrigerant circuit

Connecting air conditioner service station on vehicles with a connection on the low and high-

tion on vehicles with a connection on the low and high-pressure end of the refrig‐ erant circuit

Connecting air conditioner service station for measuring and test‐ ing

– Connect quick-release coupling adapters to the charging ho‐ ses of the air conditioner service station (handwheels not screwed in/hand shut-off valve not open).

– Switch on the air conditioner service station and evacuate the charging hoses (only necessary if there is air in the charging hoses).

– Switch off air conditioner service station.

– Unscrew the sealing caps from the service connections (with valve).

– Connect up the air conditioner service station via the service connections with quick-release coupling adapters to the vehi‐ cle refrigerant circuit.

To ensure safe operation, only tighten the handwheel of the quick-release coupling adapters enough to reliably open the valves at the refrigerant circuit connection Always monitor the pressure gauge and avoid opening the valves more than necessary.

– Perform the intended tests and measurements.

Connecting air conditioner service station on vehicles with no connection on the low-pressure

tion on vehicles with no connection on the low-pressure end of the refrigerant circuit

Certain vehicles lack a service connection for the air conditioner service station on the low-pressure side of the refrigerant circuit To connect the air conditioner service station to these vehicles' refrigerant circuits, specific adapters are necessary.

♦ Audi 80, Audi Cabriolet, Audi Coupé

For vehicles lacking a connection to the air conditioning compressor or where access is restricted, remove the low-pressure switch for the air conditioning system (F73) To bypass this switch, jumper the contacts in its connector and attach an adapter to the connection.

♦ The tools listed below are commercially available or can be obtained from the regional sales centre or importer.

♦ Should it be necessary to measure pressures at switch con‐ nections on high-pressure side, use adapter from adapter set for refrigerant circuit -V.A.G 1785/9- and proceed in the same manner.

♦ Connecting air conditioner service station to refrigerant circuit with adapter set for refrigerant circuit -V.A.G 1786-

♦ Connecting air conditioner service station to refrigerant circuit with adapter V.A.G 1785/10 ⇒ page 101

♦ Connecting air conditioner service station for measuring and testing ⇒ page 101

6.2.1 Connecting air conditioner service sta‐ tion to refrigerant circuit with adapter set for refrigerant circuit -V.A.G 1786-

A - Connection with valve (small valve core) at low-pressure side of refrigerant circuit

C - Commercially available filler hose (short version with 5/8" thread on each end)

D - Adapter with service connection -V.A.G 1786/2- (for connec‐ tion of quick-release coupling of air conditioner service station

♦ Assemble adapter and filler hose as shown and start by con‐ necting to connection with valve -A-.

The V.A.G 1786/1 adapter with a union nut is specifically designed for use with connections that feature a "small" valve insert This standard connection is utilized for the low-pressure switch in air conditioning systems (F73) and has been progressively implemented since October 1994 for air conditioner compressors.

♦ Instead of adapter with union nut -V.A.G 1786/1- , you can also use adapter -V.A.G 1785/10- (remove valve from adapter -

V.A.G 1785/10- or install valve opener in filler hose).

6.2.2 Connecting air conditioner service sta‐ tion to refrigerant circuit with adapter

– Unscrew the sealing cap from the connection with valve -A-

(at the air conditioner compressor).

– Attach an O-ring -B- to the connection (8.9 mm; 1.8 mm).

– Install valve opener -D- with appropriate seal in filler hose connection.

♦ The type of valve opener -D- and seals required depends on the filler hose used (specific to manufacturer).

♦ The quick-release coupling adapter is not required for con‐ nection on the low-pressure side of Audi vehicles.

♦ Screw filler hose -E- (to air conditioner service station) onto adapter - V.A.G 1785/10-

To minimise the amount of air and moisture ingressing into the charging hoses and thus into the refrigerant circuit, the charging hoses should be connected together as illustrated.

A - Filler hose to air conditioner service station

C - Filler hose (short version) with valve opener for connection to adapter -D-

E - Filler hose (short version) with quick-release coupling adapter

(for vehicles with quick-release coupling adapter on low-pressure side)

– Perform planned tests and measurements.

6.2.3 Connecting air conditioner service sta‐ tion for measuring and testing

– Assemble adapter set and screw onto connection on low- pressure side.

– Connect quick-release coupling adapters to the charging ho‐ ses of the air conditioner service station (handwheels not screwed in/hand shut-off valve not open).

– Switch on the air conditioner service station and evacuate the charging hoses (only necessary if there is air in the charging hoses).

– Switch off air conditioner service station.

– Unscrew the sealing cap from the service connection or the connection with valve (or remove the low-pressure switch and jumper the corresponding electrical connections).

– Connect up the air conditioner service station via the service connections with quick-release coupling adapters to the vehi‐ cle refrigerant circuit.

To ensure safe operation, only tighten the handwheel of the quick-release coupling adapters enough to reliably open the valve at the refrigerant circuit connection; be sure to monitor the pressure gauge and avoid over-opening the valve.

– Perform the intended tests and measurements.

♦ Checking the pressures in the refrigerant circuit (with the air conditioner service station) with the ignition switched off

♦ Checking pressures on vehicles with a restrictor and reservoir

(with internally regulated air conditioner compressor)

♦ Checking pressures on vehicles with an expansion valve and receiver (with internally regulated air conditioner compressor)

♦ Checking pressures on vehicles with restrictor, reservoir and air conditioner compressor regulating valve -N280- (externally regulated air conditioner compressor) ⇒ page 118

♦ Checking pressures on vehicles with expansion valve, receiv‐ er and air conditioner compressor regulating valve -N280-

(externally regulated air conditioner compressor)

Checking pressures in refrigerant circuit with air conditioner service station (with ignition

with air conditioner service station (with ignition switched off)

♦ All test requirements marked with an * are vehicle-specific and are described in the Workshop Manual for the relevant vehicle.

♦ Connections with valve and service connections for measure‐ ment and testing ⇒ Heating, air conditioning; Rep gr 87 or

⇒ Air conditioning; Rep gr 87 (vehicle-specific workshop manual).

The air conditioner compressor may include a valve at its high-pressure end to prevent liquid refrigerant from flowing back into the compressor after the system is turned off In vehicles equipped with a refrigerant circuit that has an expansion valve, this design can lead to a prolonged period before the high-pressure side's pressure drops When the system is switched off, the expansion valve becomes cold, causing the low-pressure side's pressure to rise quickly, which eventually leads to the expansion valve closing and slowing the refrigerant's flow to the low-pressure side Conversely, when the compressor is activated, the low-pressure side's pressure decreases, allowing the expansion valve to open and enabling refrigerant flow to the low-pressure end.

Residual moisture in the coolant circuit can cause ice to form at the air conditioner compressor regulating valve under specific operating conditions This ice formation disrupts the control of the air conditioner compressor, leading to excessive cooling and icing of the evaporator An iced-up evaporator can result in several operational issues.

Experiencing intermittent or complete failure of your air conditioner, resulting in a lack of cooling or heating after a long drive, can be concerning However, it's important to note that the system often resumes normal operation shortly after turning off the engine.

After a long journey, the interior windows often fog up, and pressing the defrost button may not immediately clear them However, the air conditioner resumes normal operation shortly after the engine is turned off.

For vehicles from Model Year 2001 equipped with an air conditioner compressor that includes the regulating valve -N280-, it is essential to check the evaporator output temperature sender -G263- using the "Reading measured value block" function If the measured value from the sender is found to be too low based on the customer's specified usage conditions, further investigation may be required.

At temperatures above 0 °C or below 0 °C for extended periods, the evaporator may freeze if the -N280- component is not activated Additionally, if temperatures exceed approximately 10 °C, icing can occur even when the air conditioner is operating correctly This issue can be diagnosed using a vehicle diagnostic tester.

( „self-diagnosis“ or „guided fault-finding“ function for air con‐ ditioner) and ⇒ Heating, air conditioning; Rep gr 87 or ⇒ Air conditioning; Rep gr 87 (vehicle-specific workshop manual).

– On vehicles with no evaporator output temperature sender -

To assess the output temperature using the footwell vent temperature sender (G192), set the "Lo temperature" for both the driver and front passenger sides, and adjust the fresh air blower speed to 4 or 5 bars while ensuring the air outlet is directed to the footwell in fresh-air mode If the sender's measured value is too low, particularly when the ambient temperature is above 0 °C or remains below 0 °C for an extended duration, further investigation is necessary.

– Check refrigerant pipe between evaporator and reservoir

When the engine is running, a thick pipe on the low-pressure side may indicate an issue if it is severely iced up, although a thin layer of ice is acceptable This severe icing suggests that the temperature within the evaporator is excessively low.

– Discharge refrigerant circuit, renew reservoir or receiver with dryer and then evacuate refrigerant circuit for at least 3 hours.

♦ Continuation of testing depending on design of refrigerant cir‐ cuit ⇒ page 108

• Radiator and condenser clean (clean if necessary)

• Thermal insulation at expansion valve OK and properly instal‐ led.*

• Poly V-belt OK and properly tensioned / belts for air condi‐ tioner compressor and alternator OK and properly tensioned.*

• All air ducts, covers and seals OK and properly installed.

• Electrical system and vacuum system fault-finding has not re‐ vealed any faults* ⇒ Vehicle diagnostic tester ( „self-diagno‐ sis“ or „guided fault-finding“ function for air conditioner) and ⇒

Rep gr 87 (vehicle-specific workshop manual).

The air conditioner's self-diagnosis indicates no faults when the engine is running and the air conditioner is activated Additionally, there are no compressor shut-off criteria shown in the measured value block for vehicles equipped with air conditioning self-diagnosis It is recommended to utilize a vehicle diagnostic tester with self-diagnosis or guided fault-finding functions specifically for the air conditioning system to further assess heating and cooling performance.

• Air conditioning unit not drawing in secondary air at maximum fresh-air blower speed; evaporator and heater not drawing in secondary air at maximum fresh-air blower speed*

• Air flaps in air conditioning unit, heater and evaporator reach end position*

• Fresh-air intake ducts beneath bonnet and in passenger com‐ partment as well as corresponding water drain valves OK* ⇒

• Vehicle not exposed to sunlight ⇒ Heating, air conditioning;

• All dash panel vents open

The Climatronic air conditioning system features an operating and display unit -E87- and a control unit -J255-, with an additional rear unit -E265- available for vehicles equipped with dual air conditioning systems.

– Preselect „Auto“ mode (air conditioner compressor on).

– Set „LO“ temperature for driver's and front passenger's side

(and rear left and right on vehicles with two air conditioner units).

– Press A/C button and "Rec" or recirculated air button.

– Turn the rotary temperature control towards the „cold“ stop.

– Set rotary fresh-air blower control to „4“.

Subsequently, the following system test requirements should be met:

• Operation of radiator fan(s) -V7- (at least speed 1).*

With some versions, the fan is not switched on until the pressure in the refrigerant circuit has exceeded a specified value.

• Fresh air blower -V2- (and rear fresh air blower -V80- on ve‐ hicles with two air conditioning units) run(s) at maximum speed.

• Recirculated/fresh-air flap set to „Recirculated air mode“ (with‐ in 1 min after starting vehicle, air-flow flap is closed and recirculated-air flap opened)*

• Coolant shut-off valve closed.*

• Valves of pump valve unit closed and no coolant circulation pump delivery*

• Air conditioner compressor is actually driven ( air conditioning system magnetic clutch -N25- energised, overload safeguard

The air conditioner compressor is powered by various components, such as a belt or drive shaft, depending on the engine type To ensure the protection of these components and the engine, an overload safeguard is integrated into the pulley or compressor drive unit, activating if the compressor encounters operational issues.

⇒ Heating, air conditioning; Rep gr 87 or ⇒ Air conditioning;

– Connect air conditioner service station ⇒ page 99

– Read pressures off pressure gauges; there are two possible results:

♦ The pressure in the refrigerant circuit is lower than indicated in the table.

♦ The pressure in the refrigerant circuit corresponds to that in‐ dicated in the table or is higher.

Ambient temperature (in de‐ grees centigrade) Pressure in refrigerant circuit in bar

To ensure optimal performance, the temperature of refrigerant circuit components must match the ambient temperature; deviations in temperature can lead to discrepancies in pressure values compared to standard tables.

At absolute pressure, 0 bar signifies a complete vacuum, while normal ambient pressure is represented by 1 bar absolute Notably, on most pressure gauges, 0 bar indicates an absolute pressure of 1 bar.

For vehicles equipped with a high-pressure sender (G65) or refrigerant pressure and temperature sender (G395), it is essential that the displayed pressure readings align with the specified values in the diagnostic table This can be verified using the vehicle diagnostic tester's self-diagnosis or guided fault-finding functions for the air conditioning system, as detailed in Repair Group 87.

Pressure can be measured in different units, with 1 MPa (megapascal) equating to 10 bar gauge pressure or 145 psi Additionally, 1 bar of absolute pressure is equivalent to 0 bar gauge pressure, which is approximately equal to atmospheric pressure.

The pressure in the refrigerant circuit is lower than indicated in the table.

Not enough refrigerant in circuit

– Determine refrigerant circuit leaks ⇒ page 87

– Check the pressure relief valve.

If the pressure relief valve has responded:

– Check actuation of the radiator fans.

– Check for constricted refrigerant pipe and hose cross-sections caused by inadequate bending radii.

– Check refrigerant pipes and hoses for external damage.

– If no fault is found, clean refrigerant circuit (flush with refriger‐ ant R134a ⇒ page 59 or blow out with compressed air and nitrogen ⇒ page 55 ).

The pressure in the refrigerant circuit corresponds to that indica‐ ted in the table or is higher.

– Set air conditioning system to maximum cooling output.

On vehicles with an air conditioner compressor regulating valve -

Checking pressures on vehicles with a restrictor and reservoir (with internally regulated air

restrictor and reservoir (with internally regulated air conditioner compressor)

♦ Connect air conditioner service station ⇒ page 99

– Check the pressures in the refrigerant circuit (with the air con‐ ditioner service station) with the ignition switched off

The pressures with the ignition switched off correspond to the specifications.

– Set engine speed to 2000 rpm.

– Observe the pressure reading (e.g pressure gauge) of the air conditioner service station.

♦ Switching pressures for refrigerant circuit switches are vehi‐ cle-specific.

For vehicles lacking a service connection on the low-pressure end and having an inaccessible connection at the air conditioner compressor or reservoir, the connection with the valve for the low-pressure switch or at the evaporator is essential for accurate measurements This guideline specifically applies to certain vehicles within the heating and air conditioning repair group 87 or the air conditioning repair group.

♦ Specifications for pressures in refrigerant circuit ⇒ page 109

7.2.1 Specifications for pressures in refriger‐ ant circuit

Increasing from initial pressure (on connecting pressure gauges) up to max 20 bar

Decreasing from initial pressure (on connecting pressure gauges) to value in graph

A - High pressure (measured at service connection) in bar

B - Low pressure (measured at connection with valve at air con‐ ditioner compressor or reservoir) in bar

D - Low pressure (measured at connection with valve for low- pressure switch or at service connection) in bar

Possible deviation from specification Possible causes of fault Fault elimination

• High pressure remains constant or only increases slightly (above pressure with engine stopped)

• Low pressure quickly drops to value in graph or below

• Required cooling output is not at‐ tained

Not enough refrigerant in circuit – Localise leak with leak detector and eliminate – Re-charge refrigerant circuit.

• Low pressure in line with value in graph

• Low pressure too low (see graph)

If no fault is found for this problem, clean refrigerant circuit (flush with refrigerant R134a ⇒ page 59 or blow out with compressed air and nitrogen ⇒ page 55 ).

• High pressure does not increase or only to slightly above the pres‐ sure with the engine stopped,

• low pressure does not decrease or only slightly.

♦ No actuation of the air condi‐ tioner compressor (magnetic clutch).

♦ The air conditioner compressor is not driven.

– Check actuation and drive of the air conditioner compressor and perform repair ⇒ Heating, air conditioning; Rep gr 87 or ⇒ Air conditioning; Rep gr 87

♦ Constriction or blockage in the refrigerant circuit (e.g in the re‐ frigerant pipe between the

„low-pressure end“ service connection and the air condi‐ tioner compressor).

– Clean refrigerant circuit (flush with refrigerant R134a

⇒ page 59 or blow out with com‐ pressed air and nitrogen

– Renew hose or pipe if kinked or constricted.

♦ Air conditioner compressor de‐ fective – Replace the air conditioner com‐ pressor.

• High pressure increases above specification

Constriction or obstruction in re‐ frigerant circuit – Run hand over refrigerant circuit to check for differences in tem‐ perature

• If difference in temperature is found at one component: – Renew hose or pipe if kinked or constricted.

– In the event of clogging, clean refrigerant circuit (flush with re‐ frigerant R134a ⇒ page 59 or blow out with compressed air and nitrogen ⇒ page 55 ).

• If no fault is found:

– Clean the refrigerant circuit (flush with refrigerant R134a

• High and low pressure normal at first

• After some time, high pressure increases above specification and

• Low pressure drops to value in graph or below

• Required cooling output is no lon‐ ger attained

Moisture in refrigerant circuit – Check and if necessary replace reservoir (with dryer) and re‐ strictor, then evacuate refriger‐ ant circuit for min 3 hours (see note)

– Clean the refrigerant circuit (flush with refrigerant R134a

• After lengthy operating period, low pressure drops excessively

♦ If a problem involving moisture in the refrigerant circuit only occurs after a lengthy operating period or only infrequently

When low pressure drops below specifications and the evaporator freezes, it is essential to replace the dryer and adjust the refrigerant oil quantity After these adjustments, ensure to evacuate the refrigerant circuit for a minimum of three hours.

When addressing issues in the refrigerant circuit, it is not always essential to clean the system by flushing with R134a or using compressed air and nitrogen Typically, only a minimal amount of moisture is present, which can be effectively eliminated through an extended evacuation process.

• Required cooling output is at‐ tained

Air conditioner compressor defective – Clean the refrigerant circuit (flush with re‐ frigerant R134a

⇒ page 59 or blow out with compressed air and nitrogen

– Replace the air con‐ ditioner compressor.

In the case of the fault "High pressure normal, low pressure too low," it is crucial to note that this issue can lead to evaporator icing and may cause the low-pressure switch for the air conditioning system (F73) to deactivate the air conditioner compressor, even if the refrigerant levels in the circuit are adequate.

♦ On the Audi 100, Audi A6 (up to and including Model Year

In 1997, a fault in the Audi V8 may cause the air conditioner compressor to shut off if the temperature at the fresh-air blower falls below -3 °C, impacting heating and air conditioning performance.

• High pressure normal or too high

• Low pressure too high (see graph)

Too much refrigerant in the circuit – Extract refrigerant from refrigerant cir‐ cuit.

• If quantity of refriger‐ ant extracted roughly corresponds to specified capacity: – Replace the air con‐ ditioner compressor.

• The quantity of re‐ frigerant extracted is substantially greater than the specified capacity.

– Re-charge refriger‐ ant circuit.

• High and low pressure normal

Too much refrigerant oil in the circuit – Discharge refriger‐ ant circuit.

– Clean refrigerant circuit (flush with re‐ frigerant R134a

⇒ page 59 or blow out with com‐ pressed air and ni‐ trogen ⇒ page 55 ).

♦ Overfilling with refrigerant oil may occur if, for example, the air conditioner compressor has been replaced without adjusting the quantity of refrigerant oil.

♦ If there is too much refrigerant oil in the circuit, drain the air conditioner compressor and replace the reservoir After clean‐ ing the refrigerant circuit (flush with refrigerant R134a

⇒ page 55 ), add the correct amount of refrigerant oil to the circuit ⇒ page 164

Checking pressures on vehicles with an expansion valve and receiver (with internally

expansion valve and receiver (with in‐ ternally regulated air conditioner com‐ pressor)

♦ Connecting air conditioner service station ⇒ page 99

– Set the engine speed to 2000 rpm.

♦ Switching pressures and design of refrigerant circuit switches are vehicle-specific.

♦ The pressures must be measured at the service connections; the fitting locations of these connections are vehicle-specific

• High pressure remains constant or only increa‐ ses slightly (above pres‐ sure with engine stop‐ ped)

• Required cooling output is not attained

Not enough refrigerant in circuit or expansion valve defective – Extract refrigerant from refrigerant cir‐ cuit.

• If quantity of refrigerant extracted rough‐ ly corresponds to specified capacity: – Renew expansion valve.

• The quantity of refrigerant extracted is substantially less than the specified ca‐ pacity.

– Localise leak with leak detector and eliminate

If the air conditioner is still not functioning properly after confirming no faults, it is essential to clean the refrigerant circuit by either flushing it with refrigerant R134a or using compressed air and nitrogen for a thorough blowout.

Possible devia‐ tion from speci‐ fication

Possible causes of fault Fault elimination

• High pres‐ sure does not increase or only to slightly above the pressure with the en‐ gine stop‐ ped,

• low pres‐ sure does not de‐ crease or only slightly.

• Required cooling out‐ put is not at‐ tained

♦ No actuation of the air condition‐ er compressor (magnetic clutch)

♦ The air condi‐ tioner compres‐ sor is not driven.

– Check actuation and drive of the air condi‐ tioner compressor and perform repair ⇒ Heating, air condi‐ tioning; Rep gr 87 or

Possible devia‐ tion from speci‐ fication

♦ Constriction or blockage in the refrigerant circuit (e.g in the refrig‐ erant pipe be‐ tween the „low- pressure end“ service connec‐ tion and the air conditioner com‐ pressor).

– Clean the refrigerant circuit (flush with re‐ frigerant R134a

– Replace hose or pipe if kinked or constric‐ ted.

♦ Air conditioner compressor de‐ fective.

– Replace the air con‐ ditioner compressor.

♦ Constriction or obstruction in refrig‐ erant circuit

– Run hand over refrigerant circuit to check for differences in tempera‐ ture

• If difference in temperature is found at one component:

– Renew hose or pipe if kinked or constricted.

– In the event of clogging, clean the refrigerant circuit (flush with refrig‐ erant R134a ⇒ page 59 or blow out with compressed air and nitrogen

⇒ page 55 and replace the expan‐ sion valve if applicable).

– Clean the refrigerant circuit (flush with refrigerant R134a ⇒ page 59 or blow out with compressed air and nitrogen ⇒ page 55 and replace the expansion valve if applicable). – Repeat test.

If the operation remains unsatisfactory after cleaning the refrigerant circuit—whether by flushing with refrigerant R134a or using compressed air and nitrogen—the expansion valve should be replaced.

• After some time, high pressure increases above specification and low pressure drops to value in graph or below

• Required cooling output is no longer attained

To maintain optimal performance, replace the dryer and evacuate the refrigerant circuit for a minimum of three hours Inspect the expansion valve for any dirt or corrosion, replacing it if necessary Additionally, ensure the refrigerant circuit is thoroughly cleaned by either flushing it with refrigerant R134a or blowing it out with compressed air and nitrogen.

• After lengthy operating period, low pressure drops excessively

When addressing issues in the refrigerant circuit, it is not always essential to clean the system by flushing with refrigerant R134a or using compressed air and nitrogen Typically, only a minimal amount of moisture is present, which can be effectively eliminated through an extended evacuation process.

When low pressure drops below specification and the evaporator freezes, it is essential to replace the dryer and adjust the refrigerant oil quantity After these steps, ensure to evacuate the refrigerant circuit for a minimum of three hours.

Possible deviation from specifica‐ tion Possible causes of fault Fault elimination

• High pressure normal or too high

• Low pressure too high (see graph)

• Air conditioner compressor noise (particularly after switch- on).

♦ Too much refrigerant in the circuit.

♦ Expansion valve or air condi‐ tioner compressor defective.

– Extract refrigerant from refrigerant circuit.

• If quantity of refrigerant extracted roughly corresponds to specified capacity:

– Re-charge refrigerant circuit. – Repeat test.

• The quantity of refrigerant extrac‐ ted is substantially greater than the specified capacity.

– Re-charge refrigerant circuit.– Repeat test.

If the air conditioning system fails to operate correctly upon retesting, reinstall the original expansion valve and clean the refrigerant circuit by flushing it with R134a or using compressed air and nitrogen Subsequently, replace the air conditioner compressor and receiver for optimal performance.

• High pressure only increases slightly above pressure with engine stopped

• Low pressure only drops slight‐ ly

Air conditioner compressor de‐ fective – Clean the refrigerant circuit (flush with refrigerant R134a ⇒ page 59 or blow out with compressed air and nitrogen ⇒ page 55 ).

– Replace the air conditioner com‐ pressor and receiver.

Expansion valve or air condition‐ er compressor defective – Renew expansion valve.

If the air conditioning system fails to operate correctly upon retesting, reinstall the original expansion valve and clean the refrigerant circuit by flushing it with refrigerant R134a or using compressed air and nitrogen Subsequently, replace both the air conditioner compressor and receiver for optimal performance.

♦ With this fault, the evaporator may ice up although the quantity of refrigerant in the circuit is OK.

Too much refrigerant oil in the cir‐ cuit – Discharge refrigerant circuit.

– Clean refrigerant circuit (flush with refrigerant R134a ⇒ page 59 or blow out with compressed air and nitrogen ⇒ page 55 ).

• Air conditioner compressor noise (particularly after switch- on)

♦ Overfilling with refrigerant oil may occur if, for example, the air conditioner compressor has been replaced without adjusting the quantity of refrigerant oil.

♦ If there is too much refrigerant oil in the circuit, drain the air conditioner compressor and replace the receiver After clean‐ ing the refrigerant circuit (flush with refrigerant R134a

7.4 Checking pressures on vehicles with re‐ strictor, reservoir and air conditioner compressor regulating valve -N280-

(with externally regulated air conditioner compressor)

♦ Connecting air conditioner service station ⇒ page 99

♦ The switching pressures for actuation of -N280- and the radi‐ ator fans -V7- are vehicle-specific.

Increasing from initial pressure (on connection of pressure gauges) up to 20 bar

A - Low pressure (measured at service connection) in bar abso‐ lute

B - Control current for air conditioner compressor regulating valve

In situations where there is a significant demand for cooling, such as elevated ambient temperatures and increased fresh-air blower speeds at low engine speeds, the air conditioner compressor may struggle to establish the necessary low-pressure levels initially.

The air conditioner compressor operates at maximum control current; however, its delivery volume is insufficient under certain ambient conditions and engine speeds, preventing the low-pressure side from reaching the specified pressure To evaluate the compressor's control action, one can activate the fresh-air blower at approximately 40% of its maximum voltage and assess the pressures at this reduced speed This process can be facilitated using a vehicle diagnostic tester with self-diagnosis or guided fault-finding functions for the air conditioning system, as detailed in the vehicle-specific workshop manual under Repair Group 87.

♦ Under unfavourable conditions (very high ambient tempera‐ tures, high humidity), the pressure on the high-pressure end may increase up to max 29 bar.

The control current -B- is shown in the measured value block of the Climatronic air conditioning system's operating and display unit -E87- or the Climatronic control unit -J255-.

The refrigerant circuit pressure is measured by the high-pressure sender -G65- or the refrigerant pressure and temperature sender -G395-, and this data is shown in the measured value block of the Climatronic air conditioning system -E87- or the Climatronic control unit -J255- For diagnostics, use a vehicle diagnostic tester with the "self-diagnosis" or "guided fault-finding" function for the air conditioner, as detailed in the vehicle-specific workshop manual under Heating, air conditioning; Rep gr 87.

♦ The low pressure settles as a function of the control current for the air conditioner compressor regulating valve -N280- within the air conditioner compressor output range in the tol‐ erance band.

♦ Under unfavourable conditions (very high ambient tempera‐ tures, high humidity), the air conditioner compressor output may not always be sufficient to attain the specified value.

When compressor capacity utilization exceeds 90%, the low-pressure end may experience pressures that surpass the tolerance range "C" indicated in the graph, leading to insufficient compressor output.

♦ The specified operating current for the regulating valve must be greater than 0.3 A to ensure reliable actuation of the regu‐ lating valve.

♦ At absolute pressure, „0 bar“ corresponds to an absolute vac‐ uum Normal ambient pressure corresponds to 1 bar absolute.

On the scales of most pressure gauges, 0 bar corresponds to an absolute pressure of one bar (can be seen from „-1 bar“ mark below „0“).

♦ In the "maximum cooling output" setting, the control current is regulated to approx 0.65 (vehicle-specific up to 0.85 A) (dis‐ played in measured value block) ⇒ Vehicle diagnostic tester

( „self-diagnosis“ or „guided fault-finding“ function for air con‐ ditioner) and ⇒ Heating, air conditioning; Rep gr 87 or ⇒ Air conditioning; Rep gr 87 (vehicle-specific workshop manual).

• High pressure remains constant or only increa‐ ses slightly (above pres‐ sure with engine stop‐ ped)

♦ Actuation of air conditioner com‐ pressor regulating valve -N280- not OK

♦ Not enough refrigerant in circuit

– Check actuation of -N280- – Localise leak with leak detector and eliminate

If no fault is found for this problem, clean refrigerant circuit (flush with refrigerant R134a ⇒ page 59 or blow out with compressed air and nitrogen ⇒ page 55 ).

Possible deviation from spec‐ ification Possible causes of fault Fault elimination

• High pressure does not in‐ crease or only to slightly above the pressure with the engine stopped,

• low pressure does not de‐ crease or only slightly.

♦ No actuation of the air conditioner compressor ( air conditioner compressor regulating valve - N280- )

♦ The air conditioner compressor is not driven.

– Check actuation and drive of the air conditioner compressor and perform repair ⇒ Heating, air conditioning; Rep gr 87 or ⇒ Air conditioning; Rep gr 87

♦ Constriction or blockage in the re‐ frigerant circuit (e.g in the refrig‐ erant pipe between the „low- pressure end“ service connection and the air conditioner compres‐ sor).

– Clean the refrigerant circuit (flush with refrigerant R134a ⇒ page 59 or blow out with compressed air and ni‐ trogen ⇒ page 55 ).

– Replace hose or pipe if kinked or constricted.

♦ Air conditioner compressor de‐ fective – Replace the air conditioner com‐ pressor.

♦ Constriction or obstruction in re‐ frigerant circuit

– Check actuation of -N280- – Run hand over refrigerant circuit to check for differences in temperature

• If difference in temperature is found at one component:

– Flush the refrigerant circuit with com‐ pressed air and nitrogen if clogged.

– Clean refrigerant circuit (flush with refrigerant R134a ⇒ page 59 or blow out with compressed air and nitrogen

• High and low pressure normal at first, after some time high pressure increa‐ ses above specification and

• Low pressure drops to val‐ ue in graph or below

– Check actuation of -N280- – Replace reservoir (with dryer) and evacuate refrigerant circuit for at least 3 hours (see note)

• After lengthy operating pe‐ riod, low pressure drops excessively (evaporator ices up)

When addressing issues in the refrigerant circuit, it is not always essential to flush the system with R134a or use compressed air and nitrogen for cleaning Typically, only a minimal amount of moisture is present, which can be effectively eliminated through an extended evacuation process.

When low pressure drops below specifications and the evaporator becomes iced up, it is essential to replace the dryer and adjust the refrigerant oil quantity Following this, evacuate the refrigerant circuit for a minimum of three hours to ensure proper functioning.

Issues with the evaporator output temperature sender -G263- can lead to icing in the refrigerant circuit If this issue arises, it is crucial to monitor the readings from the evaporator output temperature sender -G263- Utilize the vehicle diagnostic tester's self-diagnosis or guided fault-finding functions for the air conditioning system, and refer to the relevant sections in the workshop manual for heating and air conditioning repairs (Rep gr 87).

• Required cooling output is attained

– Check actuation of -N280- – Clean refrigerant circuit (flush with refrigerant R134a ⇒ page 59 or blow out with compressed air and nitrogen ⇒ page 55 ).

– Replace the air conditioner com‐ pressor.

Checking pressures on vehicles with expansion valve, receiver and air conditioner

pansion valve, receiver and air condi‐ tioner compressor regulating valve -

N280- (with externally regulated air conditioner compressor)

♦ Connect air conditioner service station ⇒ page 99

When diagnosing issues with a single evaporator in vehicles equipped with dual evaporators, first verify that the refrigerant circuit pressures are within acceptable limits Investigate for any restrictions or blockages in the pipe connection between the affected evaporator and the refrigerant distribution point If no faults are detected, discharge the refrigerant circuit and refill it with the correct amount of refrigerant After refilling, reassess the pressures and the air conditioner's cooling performance If the issue continues, consider replacing the expansion valve located upstream of the malfunctioning evaporator.

♦ The switching pressures for actuation of the air conditioner compressor regulating valve -N280- and the radiator fans -V7- are vehicle-specific.

A - Low pressure (measured at service connection) in bar abso‐ lute

B - Control current for air conditioner compressor regulating valve

C - Permissible tolerance range (applicable to compressor ca‐ pacity utilisation of 10 90 %).

In situations where there is a significant demand for cooling, such as during high ambient temperatures and increased fresh-air blower speeds at low engine speeds, the air conditioner compressor may struggle to establish the necessary low-pressure levels.

The air conditioner compressor operates at maximum control current, but under certain ambient conditions and engine speeds, its delivery volume may be insufficient to achieve the low-pressure values indicated in the graph To evaluate the compressor's control action in these scenarios, it's advisable to activate the fresh-air blower at approximately 40% of its maximum voltage and monitor the pressure levels at this reduced speed This can be done using a vehicle diagnostic tester equipped with self-diagnosis or guided fault-finding functions specific to air conditioning, as outlined in the vehicle-specific workshop manual under Repair Group 87.

♦ Under unfavourable conditions (very high ambient tempera‐ tures, high humidity), the pressure on the high-pressure end may increase up to max 29 bar.

♦ The control current -B- is displayed in the measured value block of the operating and display unit for Climatronic air con‐ ditioning system -E87- or the Climatronic control unit -J255-

♦ The high pressure measured by the high-pressure sender -

G65- or the refrigerant pressure and temperature sender -

G395- is displayed in the measured value block of the operating and display unit for Climatronic air conditioning sys‐ tem -E87- or the operating and display unit, Climatronic control unit -J255-

The low pressure in an air conditioning system is influenced by the control current of the compressor regulating valve (N280) and the operational characteristics of the expansion valve, all within the specified tolerance range of the compressor output.

♦ Under unfavourable conditions (very high ambient tempera‐ tures, high humidity), the air conditioner compressor output may not always be sufficient to attain the specified value.

When compressor capacity utilization exceeds 90%, the low-pressure end may experience pressures that surpass the tolerance range "C" indicated in the graph, resulting in insufficient compressor output.

♦ The specified operating current for the air conditioner com‐ pressor regulating valve -N280- must be greater than 0.3 A to ensure reliable valve actuation.

In the "maximum cooling output" mode, the control current for the air conditioner compressor regulating valve -N280- is adjusted to approximately 0.65 A, potentially reaching up to 0.85 A This specific measured value varies by vehicle and is shown in the measured value block.

♦ At absolute pressure, 0 bar corresponds to an absolute vac‐ uum Normal ambient pressure corresponds to 1 bar absolute.

In pressure gauge readings, 0 bar indicates an absolute pressure of 1 bar, as evidenced by the -1 bar mark below zero This is crucial for vehicle diagnostic testers, which utilize self-diagnosis and guided fault-finding functions specifically for air conditioning systems Additionally, it relates to heating and air conditioning repair groups, particularly in the context of automotive maintenance and service.

Possible deviation from speci‐ fication Possible causes of fault Fault elimination

• High pressure remains con‐ stant or only increases slightly (above pressure with engine stopped)

♦ Actuation of air conditioner compres‐ sor regulating valve -N280- not OK

♦ Not enough refrigerant in circuit

– Check actuation of -N280- – Extract refrigerant from re‐ frigerant circuit.

• If quantity of refrigerant ex‐ tracted is substantially less than specified capacity:

– Localise leak with leak de‐ tector and eliminate – Re-charge refrigerant circuit. – Repeat test.

• If quantity of refrigerant ex‐ tracted roughly corresponds to specified capacity:

– Renew expansion valve. – Re-charge refrigerant circuit. – Repeat test.

♦ If no fault is found for this problem, clean refrigerant circuit

(flush with refrigerant R134a ⇒ page 59 or blow out with com‐ pressed air and nitrogen ⇒ page 55 ).

Ensure to verify the readings from the evaporator output temperature sender -G263- and the operation of -N280- If the values from the evaporator output temperature sender -G263- are incorrect, it could lead to ice formation in the evaporator or insufficient cooling performance.

If the air conditioning system does not operate correctly after replacing the expansion valve, reinstall the old valve and clean the refrigerant circuit by flushing it with refrigerant R134a or using compressed air and nitrogen Subsequently, replace the air conditioner compressor and receiver to ensure optimal performance.

A defective expansion valve, whether it is permanently closed or insufficiently opened, causes the N280 component to operate at maximum output, resulting in a drop in low pressure as illustrated in the graph This situation leads to the air conditioner compressor drawing refrigerant from the low-pressure side, but since refrigerant cannot flow through the expansion valve, the desired cooling output is not achieved Consequently, the high pressure may not increase or may only experience a slight rise due to the lack of energy conversion To diagnose these issues, utilizing a vehicle diagnostic tester with self-diagnosis or guided fault-finding functions for the air conditioning system is essential.

Possible devia‐ tion from specifi‐ cation

• High pres‐ sure does not increase or only to slight‐ ly above the pressure with the engine stopped,

• low pressure does not de‐ crease or on‐ ly slightly.

• Required cooling out‐ put is not at‐ tained

♦ No actuation of the air condition‐ er compressor ( air conditioner compressor regu‐ lating valve - N280- )

♦ The air condition‐ er compressor is not driven.

– Check actuation and drive of the air conditioner com‐ pressor and per‐ form repair ⇒ Heat‐ ing, air condition‐ ing; Rep gr 87 or

♦ Constriction or blockage in the refrigerant circuit (e.g in the refrig‐ erant pipe be‐ tween the „low- pressure end“ service connec‐ tion and the air conditioner com‐ pressor).

– Clean the refriger‐ ant circuit (flush with refrigerant R134a ⇒ page 59 or blow out with compressed air and nitrogen

– Replace the air conditioner com‐ pressor.

• Low pressure quickly drops to value in graph

♦ Constriction or obstruction in re‐ frigerant circuit

– Check actuation of -N280- – Run hand over refrigerant circuit to check for differences in temperature

• If a difference in temperature is found at one component:

– In the event of clogging, clean the refrigerant circuit (flush with refriger‐ ant R134a ⇒ page 59 or blow out with compressed air and nitrogen

– Repeat the test, if the function is not OK:

– Renew expansion valve and receiv‐ er.

♦ If the function of the air conditioning system is not OK when the test is repeated, renew expansion valve and receiver.

A defective expansion valve can cause the air conditioner compressor regulating valve -N280- to operate at maximum output, resulting in a drop in low pressure as indicated in the graph Since refrigerant cannot flow through the faulty expansion valve, the cooling output is compromised, and the high pressure may not rise significantly due to a lack of energy conversion To diagnose this issue, utilize the vehicle diagnostic tester's self-diagnosis or guided fault-finding functions for the air conditioning system, as outlined in Repair Group 87.

⇒ Air conditioning; Rep gr 87 (vehicle-specific workshop manual).

♦ If there is too much refrigerant oil in the circuit, drain the air conditioner compressor and replace the receiver After clean‐ ing the refrigerant circuit (flush with refrigerant R134a

• High and low pressure nor‐ mal at first

• After some time, high pres‐ sure increases above spec‐ ification and

• low pressure drops to value in graph or below

– Check actuation of -N280- – Clean refrigerant circuit (flush with refrigerant R134a

• High and low pressure nor‐ mal at first

• After lengthy driving time, low pressure drops below specification (evaporator ices up)

– Renew receiver with dryer. – Evacuate refrigerant circuit for at least 3 hours.

When addressing issues with the refrigerant circuit, it is not always essential to perform a thorough cleaning, such as flushing with refrigerant R134a or using compressed air and nitrogen Typically, only a minimal amount of moisture is present in the system, which can be effectively eliminated through an extended evacuation process.

When low pressure drops below specifications and the evaporator becomes iced up, it is essential to replace the dryer in the receiver and adjust the quantity of refrigerant oil Following this, the refrigerant circuit should be evacuated for a minimum of three hours to ensure optimal performance.

Issues with the evaporator output temperature sender -G263- can lead to icing in the refrigerant circuit When this issue arises, it is crucial to monitor the readings from the evaporator output temperature sender -G263- Utilize the vehicle diagnostic tester for self-diagnosis or guided fault-finding functions specific to the air conditioning system, and refer to the vehicle-specific workshop manual in Repair Group 87 for further assistance.

• Required cooling output is attained

♦ Expansion valve or air conditioner compressor defective.

– Check actuation of -N280- – Clean refrigerant circuit (flush with refrigerant R134a

⇒ page 55 ) (not always nec‐ essary, refer to notes).

– Renew expansion valve and receiver.

– Re-charge refrigerant circuit. – Repeat the test, if the func‐ tion is not OK:

– Replace the air conditioner compressor.

In the case of the fault "High pressure normal, low pressure too low," it's important to note that the evaporator may experience icing, even when the refrigerant levels in the circuit are adequate.

Renewing components

• All components of the refrigerant circuit submitted for quality observation are always to be sealed (use the original sealing caps of the replacement part).

Replacement air conditioner components such as compressors, reservoirs, receivers, evaporators, and condensers have traditionally been filled with nitrogen gas However, this practice is being phased out, as the nitrogen pressure has decreased to a level where gas escape is no longer noticeable upon initial opening.

For vehicles equipped with an air conditioner compressor that lacks a magnetic clutch, the engine should only be started after the refrigerant circuit has been fully assembled, ensuring continuous operation of the air conditioner compressor.

• When the refrigerant circuit is empty, the air conditioner com‐ pressor with air conditioner compressor regulating valve -

N280- (no magnetic clutch) is switched to internal lubrication with the result that only a minimal amount of oil is pumped from the air conditioner compressor into the circuit.

Replacement parts may be stored for extended periods and in various locations, leading to the possibility of gas escaping from certain components upon initial opening while remaining contained in others.

When replacing parts with identical part numbers, it is crucial to carefully detach the sealing caps at the connections and allow the nitrogen gas to escape slowly.

♦ Refrigerant circuits are fitted either with a restrictor and reser‐ voir or with an expansion valve and receiver.

After cleaning the refrigerant circuit, it is essential to replace the dryer cartridge or components containing the desiccant bag to prevent moisture absorption Ensure that these components remain sealed for as long as possible during this process, whether flushing with refrigerant R134a or using compressed air and nitrogen.

The dryer cartridge or desiccant bag components should be replaced when performing specific repairs or if the refrigerant circuit has been open for an extended time, allowing moisture to enter, such as in the case of an accident.

The duration a refrigerant circuit can remain open without needing to replace components with a desiccant bag is significantly affected by environmental factors High ambient temperatures and humidity, as well as exposure to wet or foggy conditions, shorten this period compared to vehicles stored in a dry, heated environment Additionally, the size of the opening through which moisture can enter the circuit also plays a crucial role in determining how long the refrigerant circuit can be left open.

♦ Seal open connections and pipes (to prevent absorption of moisture).

♦ Contaminated refrigerant oils must be disposed of as used oils of unknown origin ⇒ Audi-ServiceNet, HSO Environ‐ mental Protection

♦ Leaking or damaged components (except air conditioner com‐ pressor, reservoir or receiver) ⇒ page 138

♦ Leaking or damaged components (except air conditioner com‐ pressor, reservoir or receiver) ⇒ page 139

♦ Replacing air conditioner compressor without the need for re‐ frigerant circuit cleaning ⇒ page 140

♦ Replacing air conditioner compressor on account of leakage or internal damage ⇒ page 141

♦ Renewing receiver or reservoir and restrictor after cleaning refrigerant circuit ⇒ page 141

♦ Replacing receiver or reservoir without the need for refrigerant circuit cleaning ⇒ page 143

♦ Replacing dryer cartridge/desiccant bag without the need for refrigerant circuit cleaning ⇒ page 143

8.1.1 Leaking or damaged components (ex‐ cept air conditioner compressor, reser‐ voir or receiver)

Refrigerant circuit completely empty (e.g in the event of major leakage or a burst hose)

♦ In the event of only a minor leak with slow escape of refrigerant

(e.g at a small leakage point), the amount of refrigerant oil lost and the amount of moisture ingressing is not sufficient to in‐ fluence operation of the air conditioner.

♦ The operations marked * are only to be implemented in the case of a major leak (e.g following an accident).

– Remove the air conditioner compressor.*

– Remove the oil drain plug -B- / -D- from the air conditioner compressor -A-.*

♦ The design of the oil drain plug -B- / -D- and the seal -C- /

-E- varies (depending on the air conditioner compressor man‐ ufacturer).

When installing the oil drain plug, it is crucial to adhere to the specified tightening torque, which may vary based on the air conditioner compressor manufacturer and the design of the plug Ensure compliance with the appropriate repair group guidelines for heating and air conditioning, specifically Rep gr 87 or the relevant air conditioning repair group.

♦ On the „Denso“ or „Nippondenso“ air conditioner compressor, the oil drain plug -D- is fitted with a sealing ring -E- for example; always replace ⇒ Electronic parts catalogue

♦ On the „Sanden“ or „Zexel“ air conditioner compressor, the oil drain plug -B- is fitted with an O-ring -C- for example; always replace ⇒ Electronic parts catalogue

♦ To accelerate drainage of the refrigerant oil, crank the air con‐ ditioner compressor by way of the magnetic clutch plate for example.

♦ Pour the old refrigerant oil out of the air conditioner compres‐ sor* (disposal ⇒ Audi-ServiceNet, HSO Environmental Pro‐ tection ).

♦ Then fill the air conditioner compressor with the quantity of fresh refrigerant oil corresponding to the quantity of refrigerant oil in the replacement compressor ⇒ page 164 *

♦ Use different refrigerant oils and quantities for the various air conditioner compressors ⇒ page 164

To guarantee proper lubrication of the air conditioner compressor during start-up, it is essential to add a minimum of 80 cm³ of refrigerant oil into the compressor Any additional oil can be placed into the new reservoir or receiver.

♦ If dirt has ingressed into the air conditioner compressor with the refrigerant circuit open (e.g after an accident), the air con‐ ditioner compressor is to be replaced.

♦ Clean refrigerant circuit (flush with refrigerant R134a

⇒ page 59 or blow out with compressed air or nitrogen

– Renew dryer cartridge, receiver* or reservoir* and restrictor.

– Assemble, evacuate and re-charge refrigerant circuit.

8.1.2 Leaking or damaged components (ex‐ cept air conditioner compressor, reser‐ voir or receiver)

Refrigerant circuit still contains refrigerant (e.g minor leak)

– Remove the defective component, blow out with compressed air and collect the refrigerant oil escaping.

The new component requires the addition of refrigerant oil, specifically the amount that was expelled, plus an additional 20 cm³ for the evaporator and 10 cm³ for the condenser, refrigerant pipes, and hoses.

Disposal of old refrigerant ⇒ Audi-ServiceNet, HSO Environmen‐ tal Protection

– Assemble, evacuate and charge refrigerant circuit.

8.1.3 Replacing air conditioner compressor without the need for refrigerant circuit cleaning

Cleaning refrigerant circuit means flushing with refrigerant R134a

⇒ page 59 or blowing out with compressed air or nitrogen

For example in the case of external damage following an accident

– Remove the air conditioner compressor.

– Remove the oil drain plug from the air conditioner compressor.

There are different versions of the oil drain plug and the corre‐ sponding seal (an O-ring or a sealing ring may be fitted, always replace) ⇒ page 138 and ⇒ Electronic parts catalogue

– To accelerate drainage of the refrigerant oil, crank the air con‐ ditioner compressor by way of the magnetic clutch plate for example.

– Pour the old refrigerant oil out of the air conditioner compres‐ sor (for disposal, refer to ⇒ Audi-ServiceNet, HSO Environ‐ mental Protection ).

To replace the air conditioner compressor, first, remove the oil drain plug from the defective unit and pour out the refrigerant oil Then, add a fresh refrigerant oil quantity that matches the amount you just removed from the old compressor.

To properly prepare the new air conditioner compressor, add 70 cm³ of refrigerant oil, which can be sourced from the oil drained from the replacement compressor, considering that 70 cm³ was removed from the defective unit and 220 cm³ from the replacement Ensure that the oil level is appropriate for optimal performance.

♦ Use different refrigerant oils and quantities for the various air conditioner compressors ⇒ page 144

If more than approximately 80 cm³ of refrigerant oil has leaked from the faulty air conditioner compressor, the remaining oil can be added to the evaporator or the reservoir/receiver.

8.1.4 Replacing air conditioner compressor on account of leakage or internal dam‐ age

For example due to noise from the air conditioner compressor or no air conditioner compressor output

In case of internal damage to the air conditioner compressor, it is essential to inspect the refrigerant hoses and condenser for any contamination, such as swarf If contamination is found, clean the refrigerant hoses and condenser by flushing with refrigerant R134a or using compressed air or nitrogen Additionally, replace the refrigerant hoses if needed to ensure optimal performance.

In vehicles equipped with two evaporators, the refrigerant circuit may contain more refrigerant oil than what is present in the replacement compressor Therefore, it is essential to add the additional refrigerant oil to the refrigerant circuit as needed to ensure optimal performance.

– Renew dryer cartridge, receiver or reservoir and restrictor.

– Check expansion valve for dirt or corrosion and renew if nec‐ essary

8.1.5 Renewing receiver or reservoir and re‐ strictor after cleaning refrigerant circuit

Cleaning refrigerant circuit means flushing with refrigerant R134a

⇒ page 59 or blowing out with compressed air or nitrogen

For example on account of ingress of moisture (refrigerant circuit open for lengthy period) or contamination

– Clean refrigerant circuit (flush with refrigerant R134a

⇒ page 59 or blow out with compressed air or nitrogen

– Check expansion valve for dirt or corrosion and renew if nec‐ essary

– Remove the oil drain plug from the air conditioner compressor.

There are different versions of the oil drain plug and the corre‐ sponding seal (an O-ring or a sealing ring may be fitted, always replace) ⇒ page 138 and ⇒ Electronic parts catalogue

– To accelerate drainage of the refrigerant oil, crank the air con‐ ditioner compressor by way of the magnetic clutch plate for example.

– Pour the old refrigerant oil out of the air conditioner compres‐ sor.

Disposal of old refrigerant ⇒ Audi-ServiceNet, HSO Environmen‐ tal Protection

Capacities for refrigerant R134a

♦ When charging refrigerant circuits on the high-pressure end, always fill as far as the upper tolerance limit (liquid refrigerant remains in the charging hoses).

To ensure accurate refrigerant charging in air conditioning systems, the service station must be positioned at the same level as the vehicle, with a maximum height difference of 50 cm Significant height discrepancies can cause inconsistencies between the displayed and actual refrigerant quantities Additionally, the filling precision of the service station may vary based on its design.

♦ For air conditioner compressor assignment ( „Zexel / Valeo“,

„Sanden“ or „Denso / Nippondenso“), refer to the ⇒ Electronic parts catalogue and ⇒ Heating, air conditioning; Rep gr 87 or ⇒ Air conditioning; Rep gr 87 (vehicle-specific workshop manual).

When converting refrigerant circuits from R12 to R134a, it is essential to fill the system with the quantity specified in the Workshop Manual for air conditioners using R12 Please note that this Workshop Manual is only available in hard copy.

♦ ⇒ „9.1.3 Capacities for Audi A3 (8L_) 1997 ► and Audi TT (8N_)

♦ ⇒ „9.1.5 Capacities for Audi TT (8J_) 2007 ►“, page 150

♦ ⇒ „9.1.6 Capacities for Audi 80 (8A_ / 8C_), Audi Coupé (8B_),

♦ ⇒ „9.1.8 Capacities for Audi A4 (8E_) 2001 ►, Audi A4 Cab‐ riolet (8H_) 2003 ►“, page 153

♦ ⇒ „9.1.9 Capacities for Audi A4 (8K_) 2008 ►, Audi A5 Coupé and Sportback (8T_) 2008 ►, Audi Q5 (8R_) 2008 ►, Audi A5

♦ ⇒ „9.1.10 Capacities for Audi 100 / Audi A6 (4A_) ► 1998“, page 154

♦ ⇒ „9.1.11 Capacities for Audi A6 (4B_) 1998 ► and Audi allroad

• „Denso“, „Sanden“ (or „Delphi“) air conditioner compressor with air conditioner compressor regulating valve -N280- ⇒

Heating, air conditioning; Rep gr 87 and ⇒ Electronic parts catalogue

Vehicle model Production period Capacity in grammes Differing characteristics of this refrigerant circuit

♦ Various air conditioner compressors have been fitted depend‐ ing on the production period and engine (these air conditioner compressors have no magnetic clutch).

♦ At the start of production, „Denso“ type „6 SEU 14C“ or „San‐ den“ type „7 PXE 16“ air conditioner compressors were fitted

⇒ Electronic parts catalogue and ⇒ Heating, air conditioning;

♦ Depending on the engine, „Delphi“ type „6 CVC 140“ air con‐ ditioner compressors may also be fitted at a later date (intro‐ duction not yet finalised) ⇒ Electronic parts catalogue and ⇒

Heating, air conditioning; Rep gr 87

• „Denso“ air conditioner compressor with no magnetic clutch and with air conditioner compressor regulating valve -N280-

Audi A2 From 06.00 to 07.01 525 + / - 25 • Yellow-coloured restric‐ tor

From 07.01 onwards 500 + / - 25 • Red-coloured restrictor

♦ Replacement restrictors with different holes are available (yel‐ low-coloured 1.54 mm, red-coloured 1.42 mm).

♦ Depending on manufacturer, colour of red restrictor may tend more towards orange.

♦ To avoid altering the cooling output of the air conditioner, re‐ strictors with the same hole diameter must always be used.

♦ A restrictor with a smaller hole (red-coloured) and a condenser with a smaller internal volume are installed from model year

2002 onwards The capacity has therefore been slightly modi‐ fied (condenser -70 g, smaller restrictor +50 g) ⇒ Heating, air conditioning; Rep gr 87 and ⇒ Electronic parts catalogue

• „Sanden“ or „Zexel / Valeo“ air conditioner compressor ⇒

Vehicle model Production period Capacity in grammes Differing characteristics of this refrigerant circuitAudi A3 From 08.96 onwards 750 + 50 • None

♦ Exclusive use was made at the start of production of „Sanden“ air conditioner compressors With effect from Model Year

1999, use has also been made of „Zexel / Valeo“ air condi‐ tioner compressors ⇒ Heating, air conditioning; Rep gr 87 and ⇒ Electronic parts catalogue

♦ If no replacement condenser with a flat tube width = 20 mm is available for an Audi A3 and a condenser with a flat tube width

= 16 mm is fitted, only 650 + / - 20 g of refrigerant are to be added instead of 750 + 50 g In addition the capacity given on the label must be altered accordingly (heed notes on Audi TT

Audi TT From 10.98 to 10.03 (and from

750 + 50 • Condenser with a flat tube width of 20 mm

650 + / - 20 • Condenser with a flat tube width of 16 mm

♦ The air conditioner compressor designation „Zexel / Valeo“ was changed as of 2006 to „Valeo“.

♦ With effect from 10.03 (as of vehicle identification number

8N41015239), production of the Audi TT was switched from the condenser with part no „1J0 820 411 J“ (with a flat tube width of 20 mm) to the condenser with part no „ 8N0 820 411

A“ (with a flat tube width of 16 mm) ⇒ page 148 In the period between 06.04 and 08.04, a certain number of vehicles was again fitted with condensers with a flat tube width of 20 mm.

♦ Condensers with a flat tube width = 16 mm must be filled with approx 120 g less refrigerant than condensers with a flat tube width = 20 mm ⇒ Electronic parts catalogue

♦ In the period between 10.03 (vehicles as of vehicle identifica‐ tion number 8N41015239) and 06.04, the Audi TT was fitted at the factory with a condenser with a flat tube width of 16 mm

(with part no „ 8N0 820 411 A“) and the refrigerant circuit was filled with 750 + 50 g of refrigerant These vehicles were also provided with a label indicating the wrong capacity, namely

In certain ambient conditions, such as high temperatures, over-filling the refrigerant system can lead to the air conditioner compressor shutting off due to excessive pressure This may also result in engine performance issues, including unusual sounds and increased load on the engine To remedy this, it is essential to discharge the refrigerant circuit, recharge it with the correct capacity, and update the label to reflect the accurate refrigerant amount, either by replacing it or marking the new capacity in waterproof ink.

♦ Pay attention to flat tube dimensions if condenser is renewed.

When installing a condenser with varying flat tube dimensions, it is essential to update the refrigerant R134a capacity label This can be done by either replacing the label entirely or erasing the old capacity and writing the new one in waterproof ink, as detailed in the electronic parts catalogue.

Reading flat tube dimensions of condenser

When renewing a condenser, it's crucial to consider the dimensions of the flat tube If a condenser with different dimensions is installed, ensure to replace the label indicating the refrigerant R134a capacity, or alternatively, remove the old capacity and update it with the new one using waterproof ink, as referenced in the electronic parts catalogue.

Applies to the Audi A3, Audi A3 Sportback and Audi A3 Cabriolet.

• „Denso“, „Delphi“, „Sanden“ or „Zexel / Valeo“ air conditioner compressor with air conditioner compressor regulating valve -

N280- ⇒ Heating, air conditioning; Rep gr 87 and ⇒

Vehicle model Production period Capacity in grammes Differing characteristics of this refrigerant circuit Audi A3 From 05.03 on‐ wards 525 + / - 25 • None

♦ At the start of production exclusive use was made of type „7

SEU 16“ air conditioner compressors from „Denso“ From model year 2004 onwards, a different „Denso“ compressor

(type „7 SEU 17“) has gradually been replacing the old one.

♦ With effect from Model Year 2004, „Zexel / Valeo“ (type

„DSC17E“) and „Sanden“ (type „PXE16“) air condtioner com‐ pressors were gradually introduced depending on the engine

Starting from Model Year 2008, air conditioner compressors from "Denso" (type "6 SEU 14") and "Delphi" were gradually implemented based on the engine specifications For more details, refer to the electronic parts catalogue and the heating and air conditioning section, Rep gr 87.

• „Denso“ or „Sanden“ air conditioner compressor with air con‐ ditioner compressor regulating valve -N280- ⇒ Heating, air conditioning; Rep gr 87 and ⇒ Electronic parts catalogue

Vehicle model Production period Capacity in grammes Differing characteristics of this refrigerant circuit Audi TT

03.09 onwards 500 + / - 25 • Different type of condenser fitted ⇒

Electronic parts catalogue and ⇒ Heat‐ ing, air conditioning; Rep gr 87

♦ At the start of production, exclusive use was made of air con‐ ditioner compressors of type „6 SEU 14“ manufactured by

The Denso air conditioner compressor operates without a magnetic clutch, meaning it is continuously driven by the engine Additionally, various models of air conditioner compressors can be installed later, depending on the engine specifications.

Starting from the 2008 Model Year, Sanden introduced the PXE16 air conditioner compressors for select engines, which operate without a magnetic clutch, ensuring continuous drive by the engine.

9.1.6 Capacities for Audi 80 (8A_ / 8C_), Audi Coupé (8B_), Audi Cabriolet (8G_)

• „Zexel / Valeo“ air conditioner compressor ⇒ Heating, air con‐ ditioning; Rep gr 87 and ⇒ Electronic parts catalogue

Vehicle model Production period Capacity in grammes Differing characteristics of this refrigerant circuit Audi 80

• Vehicles with 5-cyl engine • None

• Vehicles with 4 or 6-cyl engine

♦ Replacement restrictors with different holes are available If these vehicles are fitted with a yellow-coloured restrictor, add

50 g more refrigerant than specified in the table After charg‐ ing, amend capacity stated on label or affix label indicating new capacity.

♦ In order to distinguish between the two restrictor versions, the one with the smaller hole (1.54 mm) is yellow-coloured The restrictor with the larger hole (1.83 mm) is not coloured.

• „Denso“ or „Zexel / Valeo“ air conditioner compressor ⇒ Heat‐ ing, air conditioning; Rep gr 87 and ⇒ Electronic parts catalogue

Audi A4 From 11.94 to 11.97 650 + 50 • Restrictor not coloured

From 11.97 onwards 700 + 50 • Restrictor coloured (yellow)

• „Showa“ condenser (distin‐ guishing feature

From 11.98 onwards 550 + 50 • Restrictor coloured (yellow)

• „AWG“ condenser (distin‐ guishing feature

Audi RS4 From 05.00 onwards 650 + 50 • Restrictor coloured (yellow)

♦ Restrictors with a modified hole have been installed at the fac‐ tory since November 1997 (yellow-coloured) The capacity was increased by 50 g for vehicles with a yellow-coloured re‐ strictor.

♦ In order to distinguish between the two restrictor versions, the one with the smaller hole (1.54 mm) is yellow-coloured The restrictor with the larger hole (1.83 mm) is not coloured.

The Audi A4 utilized various air conditioner compressors based on the engine type and production timeframe, initially featuring "Zexel / Valeo" compressors at launch Starting in Model Year 1996, "Denso" air conditioner compressors began to be gradually integrated into vehicles equipped with 6-cylinder engines.

Replacement restrictors with various hole sizes (including uncolored, yellow, and red options) are available for vehicles When installing a different restrictor, adjust the refrigerant quantity accordingly based on the type used (refer to the table) After charging the system, update the capacity label or attach a new label reflecting the revised capacity.

♦ From November 1998 onwards, Audi A4 models have also been fitted with „AWG“ condensers (initially approx 10000 vehicles with chassis numbers between 8DXA 065 253 and

8DXA 077 026) The specified capacity for vehicles with these condensers differs from those with „Showa“ condensers The condensers can be identified on the basis of certain charac‐ teristic features ⇒ page 152

When replacing a condenser with a different part number, it is essential to verify the capacity indicated on the vehicle's label If the capacity differs, update the label accordingly or place a new label with the correct capacity over the existing one to ensure proper heating and air conditioning performance.

Rep gr 87 and ⇒ Electronic parts catalogue

Distinguishing features of „Showa“ and „AWG“ condensers

Different connections to the pressure switch.

A - Connection area on „Showa“ condenser

B - Connection area on „AWG“ condenser

9.1.8 Capacities for Audi A4 (8E_) 2001 ►, Audi A4 Cabriolet (8H_) 2003 ►

• Restrictor (yellow or red-coloured).

• „Denso“ air conditioner compressor with air conditioner com‐ pressor regulating valve -N280- (no magnetic clutch)

Vehicle model Production period Capacity in grammes Differing characteristics of this refriger‐ ant circuit Audi A4 From 11.00 onwards 500 + / - 20 • Yellow or red-coloured restrictor Audi RS4 From 07.05 onwards 440 + / - 20 • Red-coloured restrictor.

♦ Replacement restrictors with different holes are available (yel‐ low-coloured 1.54 mm, red-coloured 1.42 mm).

To maintain the air conditioner's cooling efficiency, only red or yellow restrictors should be used Yellow restrictors were installed in 2001 models, while red restrictors were introduced in 2002 It's important to note that vehicles from 2001 may also have red restrictors installed without affecting their cooling capacity.

♦ At the start of production exclusive use was made of type „6

SEU 12“ and „7 SEU 16“ air conditioner compressors from

„Denso“ From model year 2004 onwards, different „Denso“ compressors (types „6 SEU 14“ and „7 SEU 17“) have gradu‐ ally replaced the old ones ⇒ Air conditioning; Rep gr 87

(vehicle-specific workshop manual) and ⇒ Electronic parts catalogue

♦ The Audi RS 4 is fitted with a condenser with a smaller internal volume The capacity for this vehicle is therefore lower than for the other vehicles ⇒ Electronic parts catalogue

9.1.9 Capacities for Audi A4 (8K_) 2008 ►, Audi A5 Coupé and Sportback (8T_)

• Refrigerant pipe with internal heat exchanger

• „Denso“ air conditioner compressor with air conditioner com‐ pressor regulating valve -N280- ⇒ Air conditioning; Rep gr

87 (vehicle-specific workshop manual) and ⇒ Electronic parts catalogue

Vehicle model Production period Capacity in grammes Differing characteristics of this refrigerant circuit Audi A4 From 10.07 on‐ wards 600 + / - 20 • None

Audi Q5 From 09.08 on‐ wards 600 + / - 20 • None

Audi A5 Cab‐ riolet From 03.09 on‐ wards 600 + / - 20 • None

♦ The air conditioner compressors fitted at the start of production are manufactured by „Denso“ (type „6 SEU 14“) for vehicles with 4 and 6-cyl engine and type „7 SEU 17“ for vehicles with

8-cyl engine) Different makes of air conditioner compressor may also be fitted at a later date ⇒ Electronic parts catalogue and ⇒ Air conditioning; Rep gr 87 (vehicle-specific workshop manual).

The Audi RS 5 features a condenser designed with a smaller internal volume, resulting in a lower capacity compared to other models in its series For more details, refer to the electronic parts catalog.

• „Denso“ or „Zexel / Valeo“ air conditioner compressor ⇒ Heat‐ ing, air conditioning; Rep gr 87 and ⇒ Electronic parts catalogue

Vehicle mod‐ el Production period Capacity in grammes Differing characteristics of this refriger‐ ant circuit Audi 100 /

When replacing a non-colored restrictor with a yellow-colored one in a vehicle, it is essential to add an additional 50 grams of refrigerant beyond the amount specified in the guidelines Furthermore, verify the capacity indicated on the vehicle's label and update it if needed, or replace it with a new label that accurately reflects the correct capacity, ensuring it is affixed over the old label.

Since November 1997, factory-installed restrictors have featured modified holes for easy identification; the restrictor with a smaller hole measuring 1.54 mm is marked in yellow, while the larger hole version, at 1.83 mm, remains uncolored.

♦ The Audi 100 / Audi A6 features different air conditioner com‐ pressors depending on the engine and production period.

Exclusive use was made at the start of production of „Zexel /

Valeo“ air conditioner compressors As of Model Year 1996,

„Denso“ air conditioner compressors were gradually intro‐ duced for vehicles with 6-cylinder engines.

♦ The air conditioner compressor designation „Zexel / Valeo“ was changed as of 2006 to „Valeo“.

♦ From September 1994, production was gradually switched from condenser 4A0 260 403 AB to condenser 4A0 260 403

♦ The refrigerant capacity of 750+50 g applies to all Audi 100 models (regardless of condenser).

♦ Only condensers with part number 4A0 260 403 AC are now available as replacement parts (if necessary use label, part no.

Approved refrigerant oils and refrigerant oil capacities

♦ As PAG (polyalkylene glycol) oil is highly hygroscopic (attracts water), opened containers are to be immediately re-sealed so as to be air-tight.

♦ PAG oil from containers which have been open for a lengthy period is no longer usable.

♦ The oils used with refrigerant R12 are not suitable for refrig‐ erant R134a.

♦ The name of the compressor manufacturer „Nippondenso“ has been changed to „Denso“.

♦ The refrigerant oil developed specially and exclusively for

R134a refrigerant circuits is not commercially available.

♦ Refrigerant oils specifically designed for each air conditioner compressor can therefore be obtained from the replacement parts range ⇒ Electronic parts catalogue

♦ The use of other refrigerant oils may lead to system failure, as miscibility and thus also circulation with the refrigerant R134a

(for air conditioner compressor lubrication) cannot always be guaranteed.

♦ There are different refrigerant oils for „Zexel / Valeo“, „Denso“,

„Delphi“ and „Sanden“ compressors ⇒ Electronic parts cata‐ logue

♦ The refrigerant oil (G 052 300 A2) for use in refrigerant circuits with „Denso“ air conditioner compressors (old name „Nippon‐ denso“) is also included in the retrofit kit (part number 4A0 298

♦ Use is to be made for refrigerant circuits with „Zexel / Valeo“ or „Sanden“ compressor of refrigerant oil with part no G 052

♦ Use can be made for refrigerant circuits with a „Delphi“ com‐ pressor of refrigerant oil with part no G 052 154 A2 and refrigerant oil with part no G 052 300 A2 ⇒ Electronic parts catalogue

For refrigerant circuits equipped with "Zexel / Valeo" compressors, both refrigerant oils G 052 154 A2 and G 052 200 A2 can be utilized, as included in the retrofit kit (part no 4A0 298 107), as detailed in the electronic parts catalogue.

♦ For air conditioner compressor assignment ( „Zexel / Valeo“,

„Sanden“ or „Denso“), refer to the vehicle-specific workshop manual ⇒ Heating, air conditioning; Rep gr 87 or ⇒ Air con‐ ditioning; Rep gr 87 (vehicle-specific workshop manual) and

When replacing air conditioner compressors such as those from Zexel/Valeo, Denso, and Sanden, it is crucial to ensure that the refrigerant oil quantity in the new compressor matches the total amount required for optimal performance Adjusting the refrigerant oil in the replacement compressor is essential, as an incorrect oil quantity can lead to compressor damage.

When replacing an air conditioner compressor, a small amount of refrigerant oil (approximately 20 to 30 cm³) typically remains in the unit This residual oil does not impact the air conditioner's performance and can be disregarded during the replacement process.

♦ On initial switch-on, the refrigerant oil is distributed throughout the refrigerant circuit.

♦ For refrigerant oil topping-up quantities on replacing defective refrigerant circuit components, refer to ⇒ page 136 Also ⇒

Heating, air conditioning; Rep gr 87 , ⇒ Air conditioning; Rep. gr 87 (vehicle-specific workshop manual) and ⇒ Electronic parts catalogue

♦ ⇒ „9.2.5 Capacities for Audi A3 (8L_) 1997 ► and Audi TT (8N_)

♦ ⇒ „9.2.7 Capacities for Audi TT (8J_) 2007 ►“, page 171

♦ ⇒ „9.2.8 Capacities for Audi 80 (8A_ / 8C_), Audi Coupé (8B_),

♦ ⇒ „9.2.10 Capacities for Audi A4 (8E_) 2001 ►, Audi A4 Cab‐ riolet (8H_) 2003 ►“, page 173

♦ ⇒ „9.2.11 Capacities for Audi A4 (8K_) 2008 ►, Audi A5 Coupé and Sportback (8T_) 2008 ►, Audi Q5 (8R_) 2008 ►, Audi A5

♦ ⇒ „9.2.12 Capacities for Audi 100 / Audi A6 (4A_) ► 1998“, page 176

♦ ⇒ „9.2.13 Capacities for Audi A6 (4B_) 1998 ► and Audi allroad

• Air conditioner compressor from various manufacturers with air conditioner compressor regulating valve -N280- (no mag‐ netic clutch) ⇒ Heating, air conditioning; Rep gr 87 and ⇒

Vehicle model Production period Total quantity of oil in re‐ frigerant circuit in cm 3 Quantity of refrigerant oil in replacement compres‐ sor in cm 3

Differing characteristics of this refrigerant circuit

Audi A1 08.10 on‐ wards 110 + / - 10 110 + / - 10 • „Sanden“ (or „Delphi“) air conditioner com‐ pressor

When replacing an air conditioner compressor, it's essential to ensure that the new unit contains the correct amount of oil for the refrigerant circuit Adjusting the oil quantity in the compressor during replacement is crucial for optimal performance.

♦ Different air conditioner compressors are fitted depending on the production period and engine.

♦ At the start of production, „Denso“ type „6 SEU 14C“ or „San‐ den“ type „7 PXE 16“ air conditioner compressors were fitted

♦ Depending on the engine, „Delphi“ type „6 CVC 140“ air con‐ ditioner compressors may also be fitted at a later date (intro‐ duction not yet finalised) ⇒ Electronic parts catalogue and ⇒

When replacing air conditioner compressors, it's crucial to consider the oil capacities, ensuring the correct oil quantity is used for optimal performance Always refer to the specific part number and consult the electronic parts catalogue for accurate information.

♦ The different oil quantities in the air conditioner compressor may result from the design of the air conditioner compressor

When considering air conditioner compressors, whether equipped with an oil separator or not, the design of the refrigerant circuit plays a crucial role It is essential to monitor oil quantities, as excessive oil can lead to increased pressures and diminished cooling efficiency, while insufficient oil may cause lubrication issues within the compressor.

♦ The air conditioner compressor may have been fitted at the factory with a rating plate indicating the part number and the quantity of refrigerant oil in the air conditioner compressor.

• Air conditioner compressor with air conditioner compressor regulating valve -N280- (no magnetic clutch)

• „Denso“ air conditioner compressor ⇒ Heating, air condition‐ ing; Rep gr 87 and ⇒ Electronic parts catalogue

Vehicle model Production period Total quantity of oil in refrig‐ erant circuit in cm 3 Quantity of refrigerant oil in replace‐ ment compressor in cm 3

When replacing an air conditioner compressor, it is essential to ensure that the new unit contains the correct amount of oil for the refrigerant circuit Adjusting the oil quantity in the compressor after replacement is crucial for optimal performance.

To ensure optimal performance, the air conditioner compressor and engine must operate simultaneously, as the refrigerant oil is entirely contained within the compressor Therefore, it is crucial to have the entire circuit fully assembled before starting the engine.

♦ As replacement air conditioner compressors of this type are supplied with different oil capacities, the exact part no must be heeded ⇒ Electronic parts catalogue

9.2.5 Capacities for Audi A3 (8L_) 1997 ► and Audi TT (8N_) 1999 ►

• „Sanden“ or „Zexel / Valeo“ air conditioner compressor ⇒

Vehicle mod‐ el Production period Total quantity of oil in refrig‐ erant circuit in cm 3 Quantity of refrigerant oil in replace‐ ment compressor in cm 3

When replacing an air conditioner compressor, it is essential to ensure that the new unit contains the full amount of oil required for the refrigerant circuit Proper adjustment of the oil quantity in the compressor is crucial for optimal performance.

Applies to the Audi A3, Audi A3 Sportback and Audi A3 Cabriolet.

• Air conditioner compressor from various manufacturers with air conditioner compressor regulating valve -N280- (no mag‐ netic clutch) ⇒ Heating, air conditioning; Rep gr 87 and ⇒

Audi A3 From 05.03 to 10.03 180 + / - 10 180 + / - 10 • „Denso“ air conditioner compressor of „7 SEU 16“ type

From 10.03 onwards 120 + / - 10 120 + / - 10 • „Zexel / Valeo“ air con‐ ditioner compressor

110 + / - 10 110 + / - 10 • „Sanden“ air condition‐ er compressor

140 + / - 10 140 + / - 10 „Denso“ air conditioner compressor of „7 SEU 17“ type From 06.07 onwards 90 + / - 10 90 + / - 10 • „Denso“ air conditioner compressor of „6 SEU 14“ type

From 08.07 onwards 110 + / - 10 110 + / - 10 • „Delphi“ air conditioner compressor

When replacing an air conditioner compressor, it is essential to ensure that the oil quantity in the refrigerant circuit is properly adjusted, as the replacement compressor comes pre-filled with the full amount of oil required.

♦ Different air conditioner compressors are fitted depending on the production period and engine.

♦ At the start of production, exclusive use was made of air con‐ ditioner compressors of type „7 SEU 16“ from „Denso“ (e.g air conditioner compressor with part no 1K0 820 803 up to index

„D“) In Model Year 2004 (as of approx 10.03), a gradual change was made to a different type of „Denso“ compressor

( „7 SEU 17“ e.g air conditioner compressor with part no 1K0

Starting from Model Year 2004, air conditioner compressors from "Zex-el / Valeo" (type "DSC17E") and "Sanden" (type "PXE16") are being progressively integrated based on the engine specifications For more details, refer to the electronic parts catalogue.

Starting from Model Year 2008, air conditioner compressors from "Denso" (type "6 SEU 14") and "Delphi" were progressively integrated based on the engine specifications For further details, refer to the electronic parts catalogue and the heating and air conditioning section, Rep gr 87.

This air conditioner compressor serves as a replacement part and comes in various oil capacities It is crucial to ensure the correct oil quantity is used in the compressor, along with the precise part number For more information, refer to the Heating, Air Conditioning; Rep gr 87 and the Electronic Parts Catalogue.

♦ The different oil quantities in the air conditioner compressor may result from the design of the air conditioner compressor

Proper management of oil quantities in air conditioner compressors is crucial, whether using an oil separator at the high-pressure connection or not Excess oil in the refrigerant circuit can lead to increased pressures and diminished cooling efficiency, while insufficient oil may cause lubrication issues in the compressor.

♦ The air conditioner compressor may have been fitted at the factory with a rating plate indicating the part number and the quantity of refrigerant oil in the air conditioner compressor.

• „Denso“ or „Sanden“ air conditioner compressor with air con‐ ditioner compressor regulating valve -N280- (no magnetic clutch) ⇒ Heating, air conditioning; Rep gr 87 and ⇒ Elec‐ tronic parts catalogue

Audi TT From 08.06 onwards 90 + / - 10 90 + / - 10 • „Denso“ air conditioner compressor of „6 SEU 14“ type

110 + / - 10 110 + / - 10 • „Sanden“ air condition‐ er compressor

When replacing an air conditioner compressor, it is essential to ensure that the compressor contains the full amount of oil required for the refrigerant circuit Adjusting the oil quantity during replacement is crucial for optimal performance.

♦ At the start of production, exclusive use was made of air con‐ ditioner compressors of type „6 SEU 14“ manufactured by

List of testers, tools and materials

This list outlines the testers, tools and materials required for ex‐ pert refrigerant circuit repair work.

♦ Tools and materials available from regional sales centre or importer ⇒ page 189

♦ Commercially available tools and materials ⇒ page 190

10.1.1 Tools and materials available from regional sales centre or importer

Air conditioner service station with flushing kit (for currently available air conditioner service stations, refer to ⇒ V.A.G Workshop equipment cata‐ logue )

– With integrated program for flushing refrigerant circuit with refrigerant

R134a as well as the corresponding flushing kit

Refer to illustration and ⇒ V.A.G Workshop equipment catalogue

Flushing kit for refrigerant circuits (currently available flushing kits) ⇒

– For flushing the refrigerant circuit with refrigerant R134a; also for use with older air conditioner service stations with a vessel for at least 10 kg of refrigerant R134a (flushing must be performed manually)

Adapter set for refrigerant circuits -VAS 6338/1-

– For connecting air conditioner service station to refrigerant circuit and for bridging certain removed components when flushing

Leak detector V.A.G 1796 Refer to illustration

Puller for magnetic clutch (Zexel / Valeo air conditioner compressor)

Adapter set for refrigerant circuit R134a V.A.G 1785/1-10

– For connecting air conditioner service station to refrigerant circuit and for bridging certain components on flushing and blowing out

Valve adapter V.A.G 1785/9 and V.A.G 1785/10 Refer to illustration

Adapter set with service connection V.A.G 1786 Refer to illustration

Combined fine filter unit for compressed-air system (oil, dirt and water separator as used for painting facilities) ⇒ Workshop equipment cata‐ logue

O-rings ⇒ Electronic parts catalogue Refer to illustration

Refrigerant oil ⇒ Electronic parts catalogue Refer to illustration

Leak detection system VAS 6201 comprising:

♦ Hand pump with low-pressure service hose, service coupling and non- return valve VAS 6201/1

♦ UV leak detection lamp VAS 6201/4

♦ Replacement bulb for leak detection lamp VAS 6201/5

Adapter set for service connections Refer to illustration and ⇒ V.A.G

Workshop equipment catalogue Release tools for air conditioner pipes -T40149/- ⇒ V.A.G Workshop equipment catalogue Disassembly tool for refrigerant line quick-release couplings -T40232- ⇒ V.A.G Workshop Equipment catalogue

10.1.2 Commercially available tools and materials

Fin comb Refer to illustration

Charging hoses 5/8" - 18 UNF with valve opener Refer to illustration Connection piece for refrigerant cylinder and seal with quick-release coupling connection or threaded connection 5/8" - 18 UNF Refer to illustration

Valve caps 5/8"-18 UNF Refer to illustration

The nitrogen pressure gauge set includes a pressure reducer and features a quick-release coupling adapter for service connections, with two adapters provided in the air conditioner service station package Additionally, an open-ring spanner is required, sized according to the bolted joints on the refrigerant pipes.

Valve opener for charging hoses Not illustrated

Connecting nipple for conical seal 5/8"-18 UNF Not illustrated

Compressed-air gun with rubber end piece Not illustrated

Valve opener for Schrader valve Not illustrated

Hand shut-off valve 5/8"-18 UNF Not illustrated

Recycling container for refrigerant R134a Not illustrated

Refrigerant R134a with cylinder (capacity as required) Not illustrated

Filler hose with connection to compressed-air system for workshop Not illustrated

Tools and materials available from regional sales centre or importer

gional sales centre or importer

Service station / air conditioner service station (this illustration shows V.A.G 1885 for example; for currently available air condi‐ tioner service stations, refer to ⇒ V.A.G workshop equipment catalogue )

♦ The operations "testing, extraction (recycling), evacuation, flushing and charging" must be performed according to the relevant operating instructions.

Filters and dryers should be replaced at the end of their specified usage period and every time the station is drained Always have replacement filters available, which can be obtained from the equipment manufacturer For detailed guidance, refer to the operating instructions for the air conditioner service station.

♦ Air conditioner service stations not shown here can also be used ⇒ V.A.G Workshop equipment catalogue

Modern air conditioner service stations now feature a refrigerant circuit flushing program, ensuring efficient maintenance These stations come equipped with essential flushing attachments, as detailed in the V.A.G workshop equipment catalogue.

♦ This air conditioner service station incorporates the following familiar items: Charging cylinder, pressure gauge set, vacuum pump, shut-off valves and charging hoses.

♦ One quick-release coupling each (for service connections on high and low-pressure side) is included in the scope of delivery of this air conditioner service station.

♦ Depending on the version, a current vacuum display (LED) may appear after pressing the „Evacuation“ button again.

Puller for magnetic clutch V.A.G 1719 (for „Zexel / Valeo“ air con‐ ditioner compressor)

Adapter set for refrigerant circuit R134a V.A.G 1785/1-10

Adapter for cleaning refrigerant circuit (flush with refrigerant

R134a) ⇒ page 59 or blow out with compressed air and nitrogen

A - 5/8"-18 UNF thread for conical seal

B - Union nut (for connection with O-ring) with thread

A - 5/8"-18 UNF thread for conical seal

B - Internal thread with valve opener

♦ M 10 x 1.25 V.A.G 1785/9 (for connections with valve on high- pressure end)

♦ M 12 x 1.5 V.A.G 1785/10 (for connections on low-pressure end)

♦ A Schrader valve is screwed into connection -A-.

♦ A valve opener must be installed in the charging hose con‐ nection.

♦ Various adapters from this adapter set are also included in the adapter set for refrigerant circuits -VAS 6338/1-

Adapter set for service connection V.A.G 1786

A - Adapter with union nut -V.A.G 1786/1- (only for connections with small valve core at low-pressure side)

B - Filler hose with union nut 5/8"-18 UNF(short version)

♦ For connections with a large valve insert (standard on „Zexel /

Valeo“ compressors, gradual change to small valve insert as of 10.94), use is to be made of adapter V.A.G 1785/10 (remove valve from adapter V.A.G 1785/10 or install valve opener in charging hose -B-).

For removing and installing service connections and valve cores with refrigerant circuit discharged.

Commercially available tools and materials

♦ Use differently coloured charging hoses (1800 mm long).

♦ Have valve opener and spare seals to hand.

♦ A short filler hose is also included in the adapter set for refrig‐ erant circuits -VAS 6338/1-

Connection piece for refrigerant cylinder with seal, quick-release coupling connection or threaded connection 5/8" - 18 UNF

Valve caps with spare seals (for 5/8"-18 UNF thread)

Seals can also be used for charging hoses.

Valve caps with replacement seals are also included in the adapt‐ er set for refrigerant circuits -VAS 6338/1-

Pressure gauge set with pressure reducer for nitrogen (maximum reducing pressure: 15 bar).

2 - Pressure hose (ID 5 mm, length 2 m)

For connection to adapter V.A.G 1785 with 5/8"-18 UNF thread

Quick-release coupling adapter for service connections

♦ High-pressure end with nominal size 16 mm

♦ Low-pressure end with nominal size 13 mm

This quick-release coupling is included in the scope of delivery of the air conditioner service station.

Tiêu đề	Air Conditioner With Refrigerant R134a
Trường học	Audi AG
Chuyên ngành	Air Conditioning Systems
Thể loại	Service Manual
Năm xuất bản	2010
Thành phố	Ingolstadt

Định dạng
Số trang	199
Dung lượng	5,37 MB
File đính kèm	Audi TT_Type_8J_MK2_he thong dieu hoa.zip (4 MB)