Automotive Electrical and Electronic Systems Classroom Manual Fifth Edition Update by John F. Kershaw
Body Accessory Systems Operation 351SUMMARYHeating and air-conditioning systems share amotor-driven fan. The motor speeds usually arecontrolled by varying the resistance in the motorcircuit. Air-conditioning systems also have anelectromagnetic clutch on the compressor. Theclutch is energized by the air-conditioning systemcontrol switch. A clutch-cycling pressure switchturns the compressor clutch on and off as neededto maintain desired evaporator pressure and temperature.Other switches are used in the clutch circuitto protect the system from high or lowpressure, or to shut the clutch off under certainconditions, such as wide-open throttle.Older vehicles may use a fan and motor as arear-window defogger; this system is similar tothe heating system. A rear-window defroster ordefogger on late-model vehicles is a grid of conductorsattached to the rear window. A relay usuallycontrols current to the conductors. Ford’sheated windshield system uses current directlyfrom the alternator.The parts of a sound system that concern mostservice technicians include the way the sound unitand the speakers are mounted, interference capacitors,panel illumination bulbs, and power antennas.Power windows are moved by a reversible motor.Motor direction is controlled by current throughdifferent brushes. The driver’s-side master switchcontrols all of the windows, because each individualswitch is grounded through the master switch.Power seats can be moved by one, two, or threemotors and various transmission units. Permanentmagnetmotors or electromagnetic field motors canbe used. Current to the motors sometimes is controlledby a relay.Power door locks, trunk latches, and seat-backreleases can be moved by solenoids or motors.Relays are often used to control current to thesolenoid or motor.ADL systems are a safety feature integratedwith the power door locks. They automaticallylock all doors before the vehicle is driven. Keylessentry systems are both convenience and safety features:They allow a driver access to a vehicle byentering a code through a keypad on the driver’sdoor, or by depressing a button on a key chaintransmitter.Theft-deterrent systems such as the DelcoUTD and Ford Antitheft System are factoryinstalled on luxury cars. Such systems use othervehicle systems to sound an alarm when the car istampered with. The Delco VATS/PASS-Key IIsystem uses a resistor ignition key that is “read”by the lock cylinder when inserted. If the resistanceand the memory value do not match, thesystem shuts down the ignition and the starter.When engaged, the cruise control componentsset the throttle position to the desired speed. Thespeed is maintained unless heavy loads and steephills interfere. The cruise control is disengagedwhenever the brake pedal is depressed. The cruisecontrol switch is located on the end of the turnsignal lever or near the center or sides of the steeringwheel. There are usually several functions onthe switch, including off-on, resume, and engagebuttons. The switch is different for resume andnon-resume systems.The transducer is a device that controls thespeed of the vehicle. When the transducer isengaged, it senses vehicle speed and controls avacuum source (usually the intake manifold). Thevacuum source is used to maintain a certain positionon a servo. The speed control is sensed fromthe lower cable and casing assembly attached to thetransmission. The servo unit is connected to thethrottle by a rod or linkage, a bead chain, or aBowden cable. The servo unit maintains thedesired car speed by receiving a controlledamount of vacuum from the transducer. The variationin vacuum changes the position of the throttle.When a vacuum is applied, the servo spring iscompressed and the throttle is positioned correctly.When the vacuum is released, the servospring is relaxed and the system does not operate.Two switches are activated by the position ofthe brake pedal. When the pedal is depressed, thebrake release switch disengages the system. Avacuum release valve is also used to disengagethe system when the brake pedal is depressed.The Supplemental Inflatable Restraint (SIR) orair bag system includes three important elements.The electrical system includes the impact sensorsand the electronic control module. Its main functionsare to conduct a system self-check to let thedriver know that it is functioning properly, todetect an impact, and to send a signal that inflatesthe air bag. The air bag module is located in thesteering wheel for the driver and in the dash panelfor passengers. It contains the air bag and theparts that cause it to inflate. The knee divertercushions the driver’s knee from impact and helpsprevent the driver from sliding under the air bagduring a collision. It is located underneath thesteering column and behind the steering columntrim. Newer vehicles contain SIR systems in theside panels and headliner or curtains.
352 Chapter FifteenReview Questions1. Technician A says an electronic climatecontrol (ECC) system with BCM controlcycles the power to the compressor clutch.Technician B says an electronic climatecontrol (ECC) system without BCM controlcycles the ground circuit to the compressorclutch. Who is right?a. A onlyb. B onlyc. Both A and Bd. Neither A nor B2. Technician A says Ford’s heated windshieldsystem uses a conductive grid bonded tothe outside surface of the glass. TechnicianB says the conductive grid is applied tothe back of the outer glass layer before itis laminated to the inner glass layer. Whois right?a. A onlyb. B onlyc. Both A and Bd. Neither A nor B3. Constant operation of the compressor inautomotive air-conditioning systems isprevented by:a. A solenoidb. A servomagnetc. An electromagnetic clutchd. A one-way clutch4. Individual switches on automobile powerwindow circuits must be connected in______ with the driver’s side master switch.a. Seriesb. Shuntc. Paralleld. Series-parallel5. The air-conditioning compressor clutch canbe controlled by:a. A power steering cutout switchb. A pressure cycling switchc. Both A and Bd. Neither A nor B6. Technician A says the user selects themode in a semiautomatic temperaturecontrol system, but the actuators areelectrically operated. Technician B says asemiautomatic temperature control systemuses in-car and ambient temperaturesensors. Who is right?a. A onlyb. B onlyc. Both A and Bd. Neither A nor B7. Technician A says the body control module(BCM) talks to other computers in an ECCsystem on a serial data line. Technician Bsays the ECC system programmer activatesthe actuators on a serial data line. Who isright?a. A onlyb. B onlyc. Both A and Bd. Neither A nor B8. GM power seat system motors use:a. Permanent-magnet fieldsb. Electromagnetic fieldsc. Both A and Bd. Neither A nor B9. The Delphi (Delco) vehicle antitheft system(VATS) uses a _________ in the ignition key.a. Thermistorb. Potentiometerc. Magnetd. Resistor10. Power window systems use:a. Unidirectional motorsb. Reversible motorsc. Stepper motorsd. Servomotors11. Technician A says Ford’s heated windshieldsystem will work only if the in-cartemperature is above 40˚F (4˚C). TechnicianB says the heated windshield module cancontrol the EEC-IV module under certaincircumstances. Who is right?a. A onlyb. B onlyc. Both A and Bd. Neither A nor B12. Technician A says a keyless entry systemincorporates the function of an illuminatedentry system. Technician B says movingthe gear selector into Drive with theignition on activates an ADL system.Who is right?a. A onlyb. B only
- Page 313 and 314: Figure 13-32.300A wiring schematic
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- Page 325 and 326: 312 Chapter FourteenSome two-speed
- Page 327 and 328: 314 Chapter FourteenReview Question
- Page 329 and 330: 316 Chapter FifteenHEATING ANDAIR-C
- Page 331 and 332: 318 Chapter Fifteencoil. The switch
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- Page 335 and 336: 322 Chapter FifteenFigure 15-12.BCM
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- Page 347 and 348: 334 Chapter Fifteenthe heated seat
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352 Chapter Fifteen
Review Questions
1. Technician A says an electronic climate
control (ECC) system with BCM control
cycles the power to the compressor clutch.
Technician B says an electronic climate
control (ECC) system without BCM control
cycles the ground circuit to the compressor
clutch. Who is right?
a. A only
b. B only
c. Both A and B
d. Neither A nor B
2. Technician A says Ford’s heated windshield
system uses a conductive grid bonded to
the outside surface of the glass. Technician
B says the conductive grid is applied to
the back of the outer glass layer before it
is laminated to the inner glass layer. Who
is right?
a. A only
b. B only
c. Both A and B
d. Neither A nor B
3. Constant operation of the compressor in
automotive air-conditioning systems is
prevented by:
a. A solenoid
b. A servomagnet
c. An electromagnetic clutch
d. A one-way clutch
4. Individual switches on automobile power
window circuits must be connected in
______ with the driver’s side master switch.
a. Series
b. Shunt
c. Parallel
d. Series-parallel
5. The air-conditioning compressor clutch can
be controlled by:
a. A power steering cutout switch
b. A pressure cycling switch
c. Both A and B
d. Neither A nor B
6. Technician A says the user selects the
mode in a semiautomatic temperature
control system, but the actuators are
electrically operated. Technician B says a
semiautomatic temperature control system
uses in-car and ambient temperature
sensors. Who is right?
a. A only
b. B only
c. Both A and B
d. Neither A nor B
7. Technician A says the body control module
(BCM) talks to other computers in an ECC
system on a serial data line. Technician B
says the ECC system programmer activates
the actuators on a serial data line. Who is
right?
a. A only
b. B only
c. Both A and B
d. Neither A nor B
8. GM power seat system motors use:
a. Permanent-magnet fields
b. Electromagnetic fields
c. Both A and B
d. Neither A nor B
9. The Delphi (Delco) vehicle antitheft system
(VATS) uses a _________ in the ignition key.
a. Thermistor
b. Potentiometer
c. Magnet
d. Resistor
10. Power window systems use:
a. Unidirectional motors
b. Reversible motors
c. Stepper motors
d. Servomotors
11. Technician A says Ford’s heated windshield
system will work only if the in-car
temperature is above 40˚F (4˚C). Technician
B says the heated windshield module can
control the EEC-IV module under certain
circumstances. Who is right?
a. A only
b. B only
c. Both A and B
d. Neither A nor B
12. Technician A says a keyless entry system
incorporates the function of an illuminated
entry system. Technician B says moving
the gear selector into Drive with the
ignition on activates an ADL system.
Who is right?
a. A only
b. B only
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