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OBJECTIVES
After studying Chapter 24, the reader should be able to:
1. Prepare for ASE Electrical/Electronic Systems (A6)
certification test content area “G” (Horn and
Wiper/Washer Diagnosis and Repair) and content
area “H” (Accessories Diagnosis and Repair).
2. Describe how the horn operates.
3. List the components of a wiper circuit.
4. Explain how the blower motor can run at different
speeds.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
HORNS
• Horns are devices that
emit a loud sound, and
vehicles are equipped
with one or two horns.
FIGURE 24-1 The two horns on this vehicle
were finally located under the front bumper.
They were not visible until the vehicle was
hoisted.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
HORNS
• With a relay, the horn button on the steering wheel
or column completes a circuit to ground that closes
a relay, and the heavy current flow required by the
horn then travels from the relay to the horn.
FIGURE 24-2 A typical horn
circuit. Note that the horn button
completes the ground circuit for
the relay.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
HORNS
Horn System Diagnosis
• There are three types of horn failure:
– No horn operation
– Intermittent operation
– Constant operation
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
HORNS
Horn System Diagnosis
• If a horn does not operate at all, check for the
following:
–
–
–
–
–
Burned fuse or fusible link
Open circuit
Defective horn
Faulty relay
Defective horn switch
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
HORNS
Horn System Diagnosis
• If a horn operates intermittently, check for the
following:
– Loose contact at the switch
– Loose, frayed, or broken wires
– Defective relay
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
HORNS
Horn Service
• When a horn malfunctions, circuit tests are made to
determine if the horn, relay, switch, or wiring is the
source of the failure.
• Typically, a digital multimeter (DMM) is used to
perform voltage drop and continuity checks to
isolate the failure.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
HORNS
Horn Service
• Switch and relay.
– A momentary contact
switch is used to sound
the horn.
FIGURE 24-3 The horn switch is part of a
combination switch on some vehicles.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
HORNS
Horn Service
• Circuit Testing.
– Make sure the fuse or fusible link is good before
attempting to troubleshoot the circuit.
– On a system with a relay, test the power output circuit and
the control circuit.
– Test points on this system are similar to those of a system
with a relay, but there is no control circuit.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
HORNS
Horn Service
• Horn Replacement
– To replace a horn,
simply remove the
fasteners and lift the old
horn from its mounting
bracket.
FIGURE 24-4 Horns typically mount to be
radiator core support or bracket at the front of
the vehicle.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
HORNS
Horn Service
• Adjusting Horn Pitch
– An adjusting screw that extends through the horn
housing changes the diaphragm travel to control the
pitch.
FIGURE 24-5 An adjusting screw is
provided for setting the horn pitch
on some horns.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER AND WASHER SYSTEM
• Windshield wiper systems and circuits vary greatly
between manufacturers as well as between models.
• Accurate test specifications and circuit diagrams are
required for diagnosing the system.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER AND WASHER SYSTEM
FIGURE 24-6 A
circuit diagram is
necessary to
troubleshoot a
windshield wiper
problem.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER AND WASHER SYSTEM
• A typical combination wiper and washer system
consists of the following:
–
–
–
–
–
–
–
Wiper motor
Gearbox
Wiper arms and linkage
Washer pump
Hoses and jets
Fluid reservoir
Combination switch
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER AND WASHER SYSTEM
• The motor and gearbox
assembly connects to
the wiper switch on the
instrument panel or
steering column.
FIGURE 24-7 The motor and
linkage bolt to the body and
connect to the switch with a
wiring harness.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
• Switches in the mechanical wiper motor assembly
provide the necessary operation for “parking” and
“concealing” of the wipers.
FIGURE 24-8 (a) A typical wiper motor with the housing cover removed. The motor itself has a worm
gear on the shaft that turns the small intermediate gear, which then rotates the gear and tube assembly,
which rotates the crank arm (not shown) that connects to the wiper linkage. (b) If the brush retainer
becomes loose, the wiper motor will stop because the brushes get their ground connection through the
retainer and housing.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
• Most wiper motors use a permanent magnet motor
with a low-speed brush and a high-speed brush.
• When current flows through the high-speed brush,
there are fewer turns on the armature between the
hot and ground brushes, and therefore the
resistance is less.
• With less resistance, more current flows and the
armature revolves faster.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
FIGURE 24-9 A typical wiring diagram of a two-speed windshield wiper circuit using a
three-brush, two-speed motor. The dashed line for the multifunction lever indicates that
the circuit shown is only a part of the total function of the steering column lever.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
FIGURE 24-10 A typical
wiring diagram of a
three-speed windshield wiper
circuit using a two-brush
motor, but both a series and a
shunt field coil.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
Windshield Wiper Diagnosis
• If the wiper motor does not run at all, check for the
following:
–
–
–
–
Tripped circuit breaker
Grounded or inoperative switch
Defective motor
Circuit wiring fault
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
Windshield Wiper Diagnosis
• If the motor operates but the wipers do not, check
for the following:
– Stripped gears in the gearbox
– Loose or separated motor-to-gearbox connection
– Loose linkage to the motor connection
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
Windshield Wiper Diagnosis
• If the motor does not shut off, check for the
following:
– Defective parking switch inside the motor
– Defective wiper switch
– Poor ground connection at the wiper switch
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
Windshield Wiper Testing
• When the wiper motor
does not operate with
the linkage
disconnected, a few
simple voltmeter tests
quickly isolate the
circuit fault.
FIGURE 24-11 A
typical wiper motor
connector pin chart.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
Windshield Wiper Testing
• To test the wiper system:
1. Switch the ignition on and set the wiper switch to a
speed at which the motor does not operate.
2. Check for battery voltage available at the appropriate
wiper motor terminal for the selected speed.
3. Check that battery voltage is available at the motor side
of the wiper switch.
4. Check for battery voltage available at the power input
side of the wiper switch.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
Windshield Wiper Service
• Bulkhead-mounted
units are accessible
from under the hood,
while the cowl panel is
removed to service a
motor mounted in the
cowl.
FIGURE 24-12 The wiper motor and
linkage mount under the cowl panel on
many vehicles.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
Windshield Wiper Service
• Rear-window wiper
motors are generally
located inside the
rear door panel of
station wagons, or
the rear hatch panel
on vehicles with a
hatchback or liftgate.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
FIGURE 24-13 A single wiper arm mounts
directly to the motor on most rear wiper
applications.
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
Windshield Wiper Service
• Instrument panel
switches are either
snap-in units or are
retained by one or
more screws covered
by a snap-in bezel.
FIGURE 24-14 A typical instrument panel–
mounted windshield wiper control switch
assembly.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
Windshield Wiper Service
• Steering column wiper switches, which are
operated by controls on the end of a switch stalk,
require partial disassembly of the steering column
for replacement.
FIGURE 24-15 The wiper switch attaches to the
steering column on many vehicles.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
Pulse-Wipe Systems
• Pulse-wipe systems may rely on simple electrical controls,
such as a variable-resistance switch, or be controlled
electronically through a control module.
FIGURE 24-16 This rain sense wiper system adjusts wiper speed based on the amount of water on the windshield.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
Pulse-Wipe Systems
• A solid-state pulsewipe timer regulates
the control circuit of
the pulse relay to
direct current to the
motor at the
prescribed interval.
FIGURE 24-17 Circuit diagram of a rheostatcontrolled, electronically timed interval wiper.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
Windshield Washer Diagnosis
• Inoperative windshield washers may be caused by
the following:
–
–
–
–
–
–
–
Blown fuse
Empty reservoir
Clogged nozzle
Broken, pinched, or clogged hose
Loose or broken wire
Blocked reservoir screen
Leaking reservoir
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
Windshield Washer Diagnosis
• To quick check any
washer system, make
sure the reservoir has
sufficient fluid, then
disconnect the pump
hose and operate the
washer switch.
FIGURE 24-18 Disconnect the hose at the pump
and operate the switch to check a washer pump.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
WINDSHIELD WIPER MOTORS
Windshield Washer Service
• Washer motors are not
repairable and are simply
replaced if defective.
• Centrifugal or positivedisplacement pumps are
located on or inside the
washer reservoir tank or
cover and secured with a
retaining ring or nut.
FIGURE 24-19 Washer pumps usually install
into the reservoir and are held in place with a
retaining ring.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
RAIN SENSE WIPER SYSTEM
Parts and Operation
• The wiper switch can
be left on the sense
position all of the time
and if no rain is sensed,
the wipers will not
swipe.
FIGURE 24-20 A typical rain sensing module
located on the inside of the windshield near the
inside rearview mirror.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
RAIN SENSE WIPER SYSTEM
Parts and Operation
• The control knob is rotated to the desired wiper
sensibility level.
FIGURE 24-21 The electronics
in the rain sense wiper module
can detect the presence of
rain drops under various
lighting conditions.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
RAIN SENSE WIPER SYSTEM
Diagnosis and Service
• If there is a complaint about the rain sense wipers
not functioning correctly, check the owner’s manual
to be sure that they are properly set and adjusted.
• Also, verify that the windshield wipers are
functioning correctly on all speeds before
diagnosing the rain sensor circuits.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
BLOWER MOTOR OPERATION
• The same blower motor moves air inside the vehicle
for air conditioning, heat, and defrosting or
defogging.
• The switch gets current from the fuse panel with the
ignition switch on, then directs full battery voltage to
the blower motor for high speed and to the blower
motor through resistors for lower speeds.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
BLOWER MOTOR OPERATION
FIGURE 24-22 A typical squirrel cage
blower motor. A replacement blower motor
usually does not come equipped with the
squirrel cage blower, so it has to be
switched from the old motor.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
FIGURE 24-23 If blower motor resistors are
defective, replacement resistors are purchased
as a unit, as shown.
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
BLOWER MOTOR DIAGNOSIS
• If the blower motor does not operate at any speed,
the problem could be any of the following:
1. Defective ground wire or ground wire connection
2. Defective blower motor (not repairable; must be
replaced)
3. Open circuit in the power-side circuit, including fuse,
wiring, or fan switch
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
BLOWER MOTOR DIAGNOSIS
• If the blower motor operates normally at high speed but
not at any of the lower speeds, the problem could be
melted wire resistors or a defective switch.
FIGURE 24-24 A typical
blower motor circuit with four
speeds. The three lowest fan
speeds (low, medium-low,
and medium-high) use the
blower motor resistors to drop
the voltage to the motor and
reduce current to the motor.
On high, the resistors are
bypassed. The “high” position
on the fan switch energizes a
relay, which supplies the
current for the blower on high
through a fusible link.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
BLOWER MOTOR DIAGNOSIS
• The blower motor can
be tested using a
clamp-on DC ammeter.
FIGURE 24-25 Using a mini AC/DC clampon multimeter to measure the current draw
of a blower motor.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELECTRICAL ACCESSORY SYMPTOM GUIDE
• The following list will
assist technicians in
troubleshooting
electrical accessory
systems.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELECTRICAL ACCESSORY SYMPTOM GUIDE
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELECTRICAL ACCESSORY SYMPTOM GUIDE
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
Blower Motor Diagnosis
Step-by-Step
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
Blower Motor Diagnosis
Step-by-Step
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
cont
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
Blower Motor Diagnosis
Step-by-Step
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
cont
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
Blower Motor Diagnosis
Step-by-Step
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
cont
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
Blower Motor Diagnosis
Step-by-Step
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
cont
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
Blower Motor Diagnosis
Step-by-Step
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
cont
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
Blower Motor Diagnosis
Step-by-Step
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
cont
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
SUMMARY
1. Horn frequency can range from 1,800 to 3,550 Hz.
2. Most horn circuits use a relay, and the current
through the relay coil is controlled by the horn
switch.
3. Most windshield wipers use a three-brush, twospeed motor.
4. Windshield washer diagnosis includes checking
the pump both electrically and mechanically for
proper operation.
5. Most blower motors use resistors wired in series to
control blower motor speed.
6. A good blower motor should draw less than 20 A.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
REVIEW QUESTIONS
1. What are the three types of horn failure?
2. Explain how the horn switch is used to operate the
horn.
3. Describe how to determine if a windshield wiper
problem is electrical or mechanical.
4. Explain why a defective blower motor draws more
current (amperes) than a good motor.
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
1. Technician A says that a defective high-speed
blower motor relay could prevent high-speed
blower operation, yet allows normal operation at
low speeds. Technician B says that a defective
(open) blower motor resistor can prevent lowspeed blower operation, yet permit normal highspeed operation. Which technician is correct?
a)
b)
c)
d)
Technician A only
Technician B only
Both Technicians A and B
Neither Technician A nor B
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
1. Technician A says that a defective high-speed
blower motor relay could prevent high-speed
blower operation, yet allows normal operation at
low speeds. Technician B says that a defective
(open) blower motor resistor can prevent lowspeed blower operation, yet permit normal highspeed operation. Which technician is correct?
a)
b)
c)
d)
Technician A only
Technician B only
Both Technicians A and B
Neither Technician A nor B
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
2. To determine if a windshield wiper problem is
electrical or mechanical, the service technician
should _____.
a) Disconnect the linkage arm from the windshield wiper
motor and operate the windshield wiper
b) Check to see if the fuse is blown
c) Check the condition of the wiper blades
d) Check the washer fluid for contamination
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
2. To determine if a windshield wiper problem is
electrical or mechanical, the service technician
should _____.
a) Disconnect the linkage arm from the windshield wiper
motor and operate the windshield wiper
b) Check to see if the fuse is blown
c) Check the condition of the wiper blades
d) Check the washer fluid for contamination
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
3. A weak-sounding horn is being diagnosed.
Technician A says that a poor ground connector at
the horn itself can be the cause. Technician B says
an open relay can be the cause. Which technician
is correct?
a)
b)
c)
d)
Technician A only
Technician B only
Both Technicians A and B
Neither Technician A nor B
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
3. A weak-sounding horn is being diagnosed.
Technician A says that a poor ground connector at
the horn itself can be the cause. Technician B says
an open relay can be the cause. Which technician
is correct?
a)
b)
c)
d)
Technician A only
Technician B only
Both Technicians A and B
Neither Technician A nor B
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
4. What controls the operation of a pulse-wiper
system?
a) A resistor that controls current flow to the wiper
motor
b) A solid-state (electronic) module
c) A variable-speed gem set
d) A transistor
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
4. What controls the operation of a pulse-wiper
system?
a) A resistor that controls current flow to the wiper
motor
b) A solid-state (electronic) module
c) A variable-speed gem set
d) A transistor
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
5. Which pitch horn is used for a single horn
application?
a) High pitch
b) Low pitch
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
5. Which pitch horn is used for a single horn
application?
a) High pitch
b) Low pitch
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
6. The horn switch on the steering wheel
_____.
a)
b)
c)
d)
Sends electrical power to the horns
Provides the ground circuit for the horn
Grounds the horn relay coil
Provides power (12 V) to the horn relay
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
6. The horn switch on the steering wheel
_____.
a)
b)
c)
d)
Sends electrical power to the horns
Provides the ground circuit for the horn
Grounds the horn relay coil
Provides power (12 V) to the horn relay
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
7. A rain sense wiper system uses a rain
sensor that is usually mounted _____.
a)
b)
c)
d)
Behind the grille
Outside of the windshield at the top
Inside the windshield at the top
On the roof
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
7. A rain sense wiper system uses a rain
sensor that is usually mounted _____.
a)
b)
c)
d)
Behind the grille
Outside of the windshield at the top
Inside the windshield at the top
On the roof
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
8. Technician A says a blower motor can be tested
using a fused jumper lead. Technician B says a
blower motor can be tested using a clamp-on
ammeter. Which technician is correct?
a)
b)
c)
d)
Technician A only
Technician B only
Both Technicians A and B
Neither Technician A nor B
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
8. Technician A says a blower motor can be tested
using a fused jumper lead. Technician B says a
blower motor can be tested using a clamp-on
ammeter. Which technician is correct?
a)
b)
c)
d)
Technician A only
Technician B only
Both Technicians A and B
Neither Technician A nor B
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
9. A defective blower motor draws more
current than a good motor because _____.
a) The speed of the motor increases
b) The CEMF decreases
c) The airflow slows down, which decreases the
cooling of the motor
d) Both a and c
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
9. A defective blower motor draws more
current than a good motor because _____.
a) The speed of the motor increases
b) The CEMF decreases
c) The airflow slows down, which decreases the
cooling of the motor
d) Both a and c
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
10.Windshield washer pumps can be damaged
if _____.
a)
b)
c)
d)
Pure water is used in freezing weather
Contaminated windshield washer fluid is used
Ethylene glycol (antifreeze) is used
All of the above are used
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CHAPTER QUIZ
10.Windshield washer pumps can be damaged
if _____.
a)
b)
c)
d)
Pure water is used in freezing weather
Contaminated windshield washer fluid is used
Ethylene glycol (antifreeze) is used
All of the above are used
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
END
Diagnosis and Troubleshooting of Automotive Electrical,
Electronic, and Computer Systems, Fifth Edition
By James D. Halderman
© 2010 Pearson Higher Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458