chap51 pps Automotive technology at University of Cambridge

start Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 51, the reader should be able to: • • • Perform heating, ventilation, and airconditioning (HVAC) system service procedures Identify precautions that should be adhered to during HVAC system service Discuss proper evacuation and refrigerant recovery procedures Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 51, the reader should be able to: • • List the steps needed to be performed to retrofit an older R-12 system to R-134a Describe air-conditioning parts replacement and service procedures Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: air dam fin comb noncondensable gas O-ring seal quick-disconnect valve schrader valve • service cap Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 BLOWER MOTOR SERVICE Heater­related services include these components and operation: Blower motor and construction  If the blower motor is not  functioning, the switch, resistors, or blower motor itself may  need to be replaced. If the resistors are found to be defective,  then double­check that the current draw of the blower motor is  within factory specifications. One of the most common reasons  for a defective blower motor resistor is a defective blower motor  that has worn bushings and draws more than normal current  (amps) Relays and switches  Switches and relays can be tested by  proper operation and replaced if needed. Always follow the  vehicle manufacturer’s recommended replacement procedures Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 COOLING SYSTEM SERVICE Cooling System Thermostat Replacement  A defective (stuck open) thermostat can cause a  lack of heat from the heater. If heat “comes and goes,” check coolant level in the radiator before  replacing the thermostat. When replacing the thermostat, always follow the vehicle  manufacturer’s recommended procedures and use the designated coolant Heater Hose Replacement Check for signs of deterioration and replace as needed. Follow vehicle manufacturer’s recommended procedures Figure 51–1 Some heater hoses are best inspected by hoisting the vehicle and inspecting them from underneath the vehicle as shown Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Use the Same Length Heater Hoses Heater hoses are designed to supply warm coolant from the engine’s cooling system to the small radiator called the heater core inside the vehicle Because the heater hoses attach to the engine and the engine moves on its mounts during operation, the heater hoses are long enough to allow the engine to move without causing stress to be applied to the heater core The extra length also helps to prevent engine vibration from being transmitted to the heater core and the interior of the vehicle When replacing heater hoses, always use the old hoses as a guide and use the same length hoses Also, route the replacement hoses in the same manner as originally designed, again, to help reduce the stress to the heater core Cooling Fan  Inspect for dents, nicks, or other faults that can cause  a vibration or reduce airflow through the radiator. Check the viscous  fan clutch for leakage of silicone fluid and replace if needed Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Check the Air Dam if Overheating Occurs The air dam under the front of the vehicle is designed to force air to flow upward and through the radiator rather than travel underneath the vehicle If this air dam is broken or damaged due to contact with a parking block or other object, the engine may overheat Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 REFRIGERANT RECOVERY PROCEDURES Leak Repair Procedures  After a leak has been found, the  refrigerant should be recovered and the faulty part repaired or  replaced. Leaks at joints may need a replacement O­ring. Often, the  leak is at a component such as the evaporator, condenser, or  refrigerant line. Leaking components are usually replaced rather  than repaired Refrigerant should be recovered and not allowed to be discharged  into the atmosphere. A refrigerant recovery unit should be used to  remove the refrigerant from the vehicle, and it should be stored in a  container until it can be recycled See Figures 51–2 and 51–3 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 51–2 (a) A typical automotive air-conditioning service machine that is capable of handling both CFC-12 and HFC-134a systems (b) HFC-134a systems use quick-disconnect fittings that are larger than those used for CFC-12 systems Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Because It Fits, Does Not Mean it is Correct! Many air-conditioning systems use orifice tubes that look similar if not identical They are usually color coded for identification Always use the recommended orifice tube for the vehicle you are servicing Some examples of the various colors and sizes available include: Make Color Orifice Size (Inches) Chrysler Ford  Ford  Ford  Ford  GM  purple  red  orange  brown  green yellow  0.0605 0.0605 0.0560 0.0470  0.0505 0.0605 Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 RETROFITTING A CFC-12 SYSTEM TO A HFC-134A SYSTEM Due to environmental and cost concerns, many service technicians  are retrofitting (adapting) CFC­12 systems to HFC­134a systems.  When making the change, several tasks have to be performed: Specific service fittings must be installed Retrofit labels must be attached in a visible location PAG or ester oil must be used instead of the mineral oil A high­pressure shutoff switch must be installed that opens the  compressor clutch circuit if the pressure exceeds 410 psi Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Other changes that may or may not be necessary include: Replacing hoses Replacing O­rings Replacing the receiver­drier or accumulator Replacing pressure switches and calibrating them for  use with an HFC­134a system Replacing the condenser or compressor as required by  some vehicle manufacturers Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 When the system is recharged, the amount of HFC­134a is usually  90% of CFC­12 amount minus 4 ounces. If 30 ounces is the normal  charge of CFC­12, then 23 ounces of HFC­134a should be used  Figure 51–12 (a) When a system is retrofitted from CFC-12 to HFC-134a, the proper service fittings have to be used to help assure that cross-contamination does not occur (b) An under-hood sticker is also installed indicating that the system was retrofitted to HFC-134a and when it was done and by whom Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 COMPRESSOR SERVICE Compressor Drive Belt  Always check drive belt(s) whenever  servicing the air­conditioning system; replace as needed. If chunks  are missing from belt ribs or pieces of rubber embedded in the  pulleys, noise misinterpreted as a defective compressor can occur Compressor Clutch Service  If the compressor clutch is blue, it  indicates excessive heat generated by the slipping clutch Replace the clutch and adjust the air  gap according to service  information instructions Figure 51–13 A special tool is needed to remove and install the magnetic clutch on the air-conditioning compressor Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Compressor Removal  Steps specified by service information  usually include the following: Step #1  Remove the refrigerant from the system Step #2  Disconnect the compressor drive belt Step #3  Disconnect sensors and compressor clutch wiring  connections and label them if needed Step #4  Disconnect the suction and discharge hoses Step #5  Seal the hoses to help keep moisture and dirt from entering  the system Step #6  Remove the compressor mounting fasteners Step #7  Drain and measure the refrigerant oil from the compressor Step #8  Inspect the hose, lines, fittings, O­rings, seals, muffler, and  service valves for proper operation and repair or replace as needed  as part of the compressor service Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 An Additional Filter is Insurance If the air-conditioning compressor is found to be damaged mechanically, many experts recommend that an additional filter be installed in the refrigerant line to trap any debris that may have gotten into the system This additional filter will help prevent the new compressor from being harmed by the debris as it circulates through the system Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 CONDENSER SERVICE Inspect the condenser for airflow restriction and clean as needed.  Often a “fin comb” is needed to straighten the fins of the  condenser, which may have been bent by road debris Figure 51–14 A fin comb is used to straighten the fins on the condenser to help increase airflow and heat transfer Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 EVAPORATOR SERVICE If the evaporator has been tested and found to be clogged or  leaking, it has to be replaced. In most vehicles this is a major job  involving disassembly of the dash Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 RECEIVER/DRIER OR ACCUMULATOR/DRIER SERVICE Most experts recommend the receiver/drier or accumulator/drier be  replaced anytime the refrigerant system is opened and other repairs or  services are being performed. Before replacing the receiver/drier or  accumulator/drier, determine the quantity of refrigerant oil so that the  proper amount can be added to the system when it is recharged.  Figure51–15 Always be sure that the service valves are snug before evacuating the system They are a common place for small refrigerant leaks Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Might As Well Do It Now Whenever an evaporator is being replaced, many service technicians also recommend that the heater core also be replaced This is especially true if the vehicle had a neglected cooling system Most heater cores are close to or even have to be removed to replace an evaporator The only additional cost to the vehicle owner is the cost of the heater core itself Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 ORIFICE TUBE/EXPANSION VALVE SERVICE If the orifice tube is found to be clogged or the expansion valve  has been determined to be not operating correctly, they will  require replacement Always follow the vehicle manufacturer’s recommended  replacement procedures and adhere to all precautions Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY The proper operation of the heater depends on the proper  operation of the engine cooling system as well as the blower  motor and temperature controls A serviceable compressor drive belt and clutch are needed for  the proper operation of the air­conditioning system Refrigerant must be checked for contamination before  recovery Check for leaks in the system by drawing a vacuum on the  system and checking to see that other systems are able to  maintain the vacuum Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) Always use the specified replacement parts, such as orifice  tubes, to be assured of proper operation Verify that the heating and air­conditioning system is  functioning correctly after any repair or service Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 end Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458