chap47 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 47, the reader should be able to: • • • • Prepare for ASE Electrical/Electronic Systems (A6) certification test content area “H” (Accessories Diagnosis and Repair) Describe how AM and FM radio works Explain how to test speaker polarity Explain how to match speaker impedance 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 47, the reader should be able to: • • Explain how crossovers work List causes and corrections of radio noise and interference 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: active crossover • alternator whine • amplitude modulation (AM) bluetooth carrier wave • crossover decibels (dB) electronically tuned receiver (ETR) floating ground system • flutter • frequency • frequency modulation (FM) 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: ground plane hertz • high-pass filter • impedance low-pass filter modulation picket fencing • powerline capacitor radio choke • radio frequency (RF) • root-mean-square (RMS) 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: satellite digital audio radio services (SDARS) • sideband operation • speakers • stiffening capacitor • subwoofer total harmonic distortion (THD) • tweeter voice recognition wavelength 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 The audio system of today’s vehicles is a complex combination of antenna system, receiver, amplifier, and speakers all designed to provide living room-type music reproduction while the vehicle is traveling in city traffic or at highway speed 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 AUDIO FUNDAMENTALS There are two types of energy that affect audio systems.  Electromagnetic energy or radio waves  Antennas capture  the radio waves which are then sent to the radio or receiver to  be amplified Acoustical energy, usually called sound  Radios and  receivers amplify the radio wave signals and drive speakers  which reproduce the original sound that was transmitted by  radio waves See Figure 47­1 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 47–1 Audio systems use both electromagnetic radio waves and sound waves to reproduce sound inside the vehicle 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 Electromagnetic energy moves through the air while acoustical  energy moves air. Radio waves are measured in two ways:  wavelength and frequency. A radio wave has a series of high points  and low points A wavelength is the time and distance between two consecutive  points, either high or low, measured in meters. Frequency, also  known as radio frequency, or RF, is the number of times a  particular waveform repeats itself in a given amount of time and is  measured in hertz A signal with a frequency of one hertz is one radio wavelength per  second. Radio frequencies are measured in kilohertz, thousands of  wavelengths per second, and megahertz, millions of wavelengths  per second. See Figure 47–2 and examples following 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 Antenna  To be able to receive satellite radio, the antenna needs to  be able to receive signals from both the satellite, as well as repeater  stations located in many large cities. There are various types and  shapes of antenna, including those shown here Figure 47–22 An aftermarket XM radio antenna mounted on the rear deck lid The deck lid acts as the ground plane for the antenna Figure 47–23 A shark-fin-type factory antenna used for both XM and OnStar® 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 Most satellite radios contain temporary memory so the radio will  continue to operate even if the signal from the satellite or repeater  station is temporarily disrupted due to tall buildings or other objects Diagnosis and Service  The first step in any diagnosis is to verify  the customer complaint (concern). If no satellite service is being  received, first check with the customer to verify that the monthly  service fee has been paid and the account is up to date If poor reception is the cause, carefully check the antenna for  damage or faults with the lead­in wire For all other satellite radio fault problems, check service  information for the exact tests and procedures. Always follow the  factory recommended procedures 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 What Does ESN Mean? ESN means electronic serial number This is necessary information to know when reviewing satellite radio subscriptions Each radio has its own unique ESN 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 RADIO INTERFERENCE Radio interference is caused by variations in voltage in the  powerline or picked up by the antenna A “whine” increasing in  frequency with engine  speed is referred to as  alternator whine It is eliminated by  installing a radio choke  or a filter capacitor in  the power feed wire to  the radio.  Continued Figure 47–24 A radio choke and/or a capacitor can be installed in the power feed lead to any radio, amplifier, or equalizer 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 Ignition noise is usually a raspy sound that varies with the speed of  the engine. This noise is usually eliminated by the installation of a  capacitor on the positive side of the ignition coil. The capacitor  should be connected to the power feed wire to either the radio or the  amplifier or both.  Figure 47–25 Many automobile manufacturers install a coaxial capacitor, like this one, in the power feed wire to the blower motor to eliminate interference caused by the blower motor The capacitor must be  grounded.  If a standard automotive condenser is unavailable,  use a 470­µF 50­volt  electrolytic capacitor 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 A radio choke, which is a coil of wire, can also be used to reduce or  eliminate radio interference. Radio interference being picked up by  the antenna can best be eliminated by stopping the source by  making certain that all units containing a coil, such as electric  motors, have a capacitor or diode attached to the power­side wire Most radio interference complaints come when someone installs an  amplifier, power booster, equalizer, or other radio accessory A major cause of this interference is the variation in voltage  through the ground circuit wires. To prevent or reduce this  interference, make sure all ground connections are clean and tight Placing a capacitor in the ground circuit also may be beneficial 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 The Separate Battery Trick When diagnosing sound system interference, try running separate 14gauge wire(s) from the sound system power lead and ground to a battery outside of the vehicle If the noise is still heard, the interference is not due to a generator diode or other source in the wiring of the vehicle Radio noise can be broadcast or caused by voltage variations in the  power circuit to the radio. A capacitor and/or radio choke are most  commonly used components. A “sniffer” can be used to locate the  source of the radio noise. See Figure 47­26.  CAUTION: Amplifiers sold to boost the range or power of an antenna  often increase the level of interference and radio noise to a level that  disturbs the driver 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 47–26 A “sniffer” can be made from an old antenna lead-in cable by removing about inches of the outer shielding from the end Plug the lead-in cable into the antenna input of the radio and tune the radio to a weak station Move the end of the antenna wire around the vehicle dash area The sniffer is used to locate components that may not be properly shielded or grounded and can cause radio interference through the case (housing) of the radio 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 AUDIO NOISE SYMPTOM CHART See the chart on Page 544 of your textbook.  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 Lightning Damage A radio failed to work in a vehicle that was outside during a thunderstorm The technician checked the fuses and verified that power was reaching the radio Then the technician noticed the antenna It had been struck by lightning Obviously, the high voltage from the lightning strike traveled to the radio receiver and damaged the circuits Both the radio and the antenna were replaced to correct the problem Figure 47–27 The tip of an antenna that was struck by lightning 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 The GM Security Radio Problem - Part A customer replaced the battery in a GM vehicle and now the radio display shows “LOC” This means the radio is locked with a customer code stored To unlock the radio, the tech used the following steps (the code number being used is 4321) Step 1—Press the “HR” (hour) button—“000” is displayed Step 2—Set the first two digits using the hour button—“4300” is displayed Step 3—Set the last two digits of the code using the “MIN” (minutes) button—“4321” is displayed Step 4—Press the AM-FM button to enter the code The radio is unlocked and the clock displays “1:00.” Thankfully, the owner had the security code If the owner had lost the code, the tech would have to secure a scrambled factory backup code from the radio and then call a toll-free number to obtain another code The code will only be given to authorized dealers or repair facilities 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 The GM Security Radio Problem - Part Other displays and their meaning include: “InOP” This display indicates that too many incorrect codes have been entered and the radio must be kept powered for one hour and the ignition turned on before any more attempts can be made “SEC” This display means there is a customer’s code stored but the radio is unlocked “—” This means there is no customer code stored and the radio is unlocked “REP” Means customer’s code has been entered once and the radio now is asking that the code be repeated to verify it was entered correctly the first time 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 Radios receive AM (amplitude modulation) and FM  (frequency modulation) signals broadcast through the air The radio antenna is used to induce a very small voltage signal  as an input into the radio from the electromagnetic energy  from the broadcast station AM requires an antenna whereas FM may be heard from a  radio without an antenna Speakers reproduce the original sound, and the impedance of  all speakers should be equally matched 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.) Crossovers are used to block certain frequencies to allow each  type of speaker to perform its job better. A low­pass filter is  used to block high­frequency sounds being sent to large  woofer speakers, and a high­pass filter blocks low­frequency  sounds being sent to tweeters Radio interference can be caused by many different things,  such as a defective generator (alternator), a fault in the  ignition system, or a fault in a relay or solenoid 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