NAVEDTRA 14050a User manual

Trailer connections. Both the tractor and trailer have a seven-terminal trailer
receptacle that accepts the trailer electrical cable plug (Figure 6-54). Trailers used as a
part of double and triple trailers have trailer receptacles at both the front and rear of the
trailer to provide interconnection between trailers and dollies.
Figure 6-54 - Tractor-trailer connectors.
Because most tractors do not pull the same trailer all the time, the trailer receptacle and
cable are standardized throughout North America. The trailer interconnection is defined
by SAE recommended practice J560. Each of the seven circuits on all trucks and
trailers should be wired in the prescribed manner to permit tractors and trailers
throughout North America to be interchangeable.
NAVEDTRA 14050A 6-53

The color of wiring insulation for each trailer circuit is also standardized, as shown in
Figure 6-55. This wiring convention should be followed to aid in troubleshooting and
identification.
SAE J560 STANDARDS
Conductor
Identification Wire Color
Lamp and Signal Circuits
Wht White Ground return to towing vehicle
Blk Black Clearance, side marker & license plate
Yel Yellow Left-hand turn signal & hazard signal lamps
Red Red Stop lamps and antilock devices
Grn Green Right-hand turn signal & hazard signal lamps
Brn Brown Tail, clearance, side marker lamps, &
identification lamps
Blu Blue Auxiliary
Figure 6-55 - Trailer standard wiring colors.
Note in the schematic layout Figure 6-56 that the trailer running lights are broken down
into two circuits: the black wire and the brown wire. The black wire should be connected
to the front marker and clearance lamps, the identification lamp (three-bar light), the two
lower rear-side marker lamps, and the center marker lamps (if applicable). The brown
wire should be connected to the rear clearance lamps, the tail lamps, and the license
plate lamp. These circuits should be kept isolated from each other because they may be
protected by two different circuit protection devices in the tractor. Otherwise, a short
circuit at one place in the trailer running lamp wiring would disable all trailer running
lamps.
The illustration of the trailer plug and the trailer receptacle in Figure 6-57 is something
that you should become familiar with. It shows the views of the mating end of the tractor
receptacle and of the trailer plug. A test light or a special trailer light test tool is used to
test for voltage at the specific terminal to determine if the problem is with the truck or the
trailer. Notice the larger-diameter terminal at the top; this is the trailer ground terminal.
Because all trailer light current must pass through the ground circuit, it uses a larger-
diameter terminal than the other terminals and uses a larger-diameter wire than the
other wires in the seven-way cable.
The tractor normally provides the circuit protection for trailer wiring. However, some
trailers may have circuit breakers for trailer lights as well, (Figure-58). The trailer power
distribution module is usually mounted on the left frame rail aft of the cab or on a rear
crossmember at the end of the frame rail, as shown in Figure 6-59. The trailer PDM
contains fuses and relays to enable high current outputs via a wiring harness and relays
to enable high current outputs via a wiring harness to the trailer connector.
The length of the trailer wiring must be considered when replacing trailer wiring. Even
though the rear trailer lamps may have the same ratings as the truck lamps, the long
distance to the lamps can result in a substantial voltage drop on the wiring. This
reduces the voltage at the trailer lamps. Wire gauge is especially important for double
NAVEDTRA 14050A 6-54

and triple trailers because the total circuit from the rear trailer light feed to the tractor
can be more than 80 feet. Figure 6-60 should be used to determine the wire gauge
necessary for trailer wiring repair or replacement.
Conductor No. Color Key Lamp and Signal Circuits
1White Ground return to towing vehicle
2Black
x Side marker and identification lamps
3Yellow • Left-hand turn signal and hazard signal
4Red
Stop lamps and antilock devices
5 Green
• Right-hand turn signal and hazard
signal
6 Brown

Tail, combined rear clearance, and
license plate
7Blue
AUx Auxiliary, option lamps, dome, etc.
Figure 6-56 - Schematic layout of a trailer electrical system.
NAVEDTRA 14050A 6-55

Figure6-57 - Tractorandtrailermatingends.
Figure 6-58 - Trailer power distribution module.
NAVEDTRA 14050A 6-56

Figure6-59-TrailerPDMinstallation.
NAVEDTRA 14050A 6-57

TOTAL LENGTH OF CABLE IN CURCUIT FROM BATTERY TO MOST DISTANT
LAMP
12-Volt System
Amperes
(approx) Up to 30 Feet 40 Feet 50 Feet 60 Feet 80 Feet 100 Feet 120 Feet
Gauge Gauge Gauge Gauge Gauge Gauge Gauge
1.0 14
2 14
3 14
4 14
14 14
14 14
14 14
14 14
14 14 14 14
14 14 14 14
14 14 14 12
14 14 12 12
5 14
6 14
7 14
8 14
10 14
14 14
14 14
14 12
12 12
12 12
14 12 12 12
14 12 12 10
12 12 10 10
12 10 10 10
12 10 10 8
11 14
12 14
15 12
18 12
20 12
12 12
12 12
12 10
10 10
10 10
10 10 8 8
10 10 8 8
10 8 8 8
8 8 8 8
8 8 8 6
25 12 10 8 8 8 6 6
30 12 10 8 8 8 6 6
35 12 10 8 8 6 6 6
Recommended minimum wire gauge for stop light and ground circuits.
STOP LIGHT (Red) GROUND (White)
Single trailer (up to 50' length)
Doubles trailer (2-28' lengths)
Doubles trailer (2-40' lengths)
Triples trailer (3-28' lengths)
-12 Gauge
-12 Gauge
-10 Gauge
10 Gauge
10 Gauge
10 Gauge
8 gauge
8 gauge
Figure 6-60 - Recommended wire gauges for trailer wiring.
Figure 6-61 is a quick reference for troubleshooting electrical systems. It is always
recommended to refer to the service manual for detailed information for troubleshooting
and repairs.
NAVEDTRA 14050A 6-58

Electrical Troubleshooting
Description of Fault Possible cause
Stop lights on at all times Battery Mega Fuse that supplies the trailer
power distribution module (ODM) is open
or missing.
Trailer connector center pin (pin 7) is not
providing desired power condition Incorrect Reference Parameter
Intermittent or no electrical trailer operation
at all outputs Loss connection. Check trailer PDM
electrical connections and ground.
No operation on single output. Trailer PDM components are inoperable.
Check PDM fuse (blown) and relay (stuck)
for that output.
Intermittent or no operation on single
output Terminal connection(s) damaged wire.
Trace the suspect circuit.
Figure 6- 61 - Quick reference electrical troubleshooting.
11.5.1 Horns
The horn system uses a coil-operated diaphragm to produce sound waves and an
audible sound. The horn system is simple; it consists of:
1.
Fuseorcircuitbreaker - electricalsafetydevicethatprotectshorncircuitfrom
shorts
2. Hornwiringharness - wiresthatconnectfusetoharnessand hornstohorn
button switch
3. Horns - diaphragm-operateddevicesthatvibratetoproducesoundwaves
4.
Hornswitch - steeringwheel-orsteeringcolumn-mountedswitchforcompleting
horncircuit
Figure 6-62 shows a basic horn system. Power is present at the horns and in the
harness whenever the ignition switch is turned on. The horns switch grounds the circuit
to activate the horns.
NAVEDTRA 14050A 6-59

Figure6-62 - Horncircuit.
When the driver presses the horn
button, the wire leading from the
horns is grounded. This causes
current to flow through the fuse
and horns. The resistance in the
horn coils limits how much current
flows into ground.
When the driver releases the horn
button, a spring pushes the
switch back open. This breaks or
disconnects the ground circuit. No
current can then flow through the
horns and they stop sounding.
Horn nomenclature. A cutaway
view of a typical horn is given in
Figure 6-63. It is made up of the
following components:
1. Horn coil - set of windings
thatproducemagneticfield
whenenergizedbycurrent
flow
Figure6-63 - Cutawayviewofahorn.
NAVEDTRA 14050A 6-60

2. Contacts - breakerpointsthatopenandclosetocontrolcurrentflowthrough
horncoil
3. Diaphragm - flexiblemembraneinhornthatmovesbackandforthtoproduceair
wavesandsound
4. Plunger - metalcorethatisattachedbymagneticfieldofcoilwindings
5. Wireterminal - connectorformakingelectricalconnectionwithwiringharness
6. Outlet - openingofhornhousingfordirectingsoundtofrontofvehicle
When the driver presses the horn button, current flow enters the wire terminal and horn
coil. A magnetic field forms around the coil. The field attracts and pulls the plunger into
the coil. Since the plunger is attached to the diaphragm, the diaphragm is flexed back
toward the coil.
With enough movement, the edge of the plunger touches one of the contact point arms.
This pushes the contacts open and interrupts the current flow through the coil. Without
current, the magnetic field collapses, and the diaphragm snaps or flexes back into its
normal position.
Once the diaphragm and plunger move back, the contacts reclose. This reenergizes the
coil and the diaphragm is again pulled back toward the coil. The process is repeated
rapidly and the diaphragm vibrates back and forth in the horn housing. The resulting
vibration set up in the surrounding air can be heard as a "honking" sound.
A tone adjustment screw is normally provided for changing the sound of the horn. It can
be turned to affect the action of the contact points and frequency of the diaphragm
vibration.
Horn relay. A horn relay is sometimes used between the horn switch and the horns. It
is used to reduce the amount of current flowing through the horn switch.
When the driver presses the horn switch, a small current flow enters the horn relay. This
energizes the small coil in the relay to close the relay contacts. Then, a larger current
flows through the closed relay points and to the horns.
Horn Service. When a horn will not sound, check the fuse and connections, and test
the voltage at the horn terminal. If a horn blows continuously, the horn switch may be
bad. A relay is another cause of horn problems. The contacts in the relay could be
burned, or they may be stuck together.
A horn current adjusting screw is sometimes provided on the horn to set the amp draw
through the horn. To adjust horn current, connect an ammeter between the feed wire
and horn terminal. To prevent meter damage, be sure the ammeter can read more than
30 amps.
Get another person to sound the horn while you read the meter. If the current is not
within specifications (typically 4-5 amps), turn the amps screw on the horn until the
meter reads properly. Also, make sure you are getting adequate supply current/voltage
and there is not a high resistance in the horn circuit. If you cannot get the horn to read
within current specifications, replace it or isolate the circuit problem.
11.6.0 Small Accessory Motors
11.6.1 Windshield Wipers
A typical windshield wiper system is made up of a switch, wiper motor assembly, wiper
linkage, wiper arms, and wiper blades. Either a fuse or circuit breaker protects the
system.
NAVEDTRA 14050A 6-61

The windshield wiper switch is a multiposition switch that sometimes contains a
rheostat. Each switch position provides a different wiping speed. The rheostat operates
the delay mode for slow wiping action. A relay is frequently used to complete the circuit
between the battery and the wiper motor.
A wiper motor assembly consists of a permanent magnet motor and a transmission. The
wiper motor transmission changes rotary motion into a back-and-forth wiping motion.
The transmission is normally a set of plastic gears, an end housing, and a crank.
On the windshield wiper assembly the drive crank on the transmission connects to the
wiper linkage.
The wiper linkage is a set of arms that transfers motion from the wiper motor
transmission to the wiper arms. The rubber wiper blades fit on the wiper arms.
Windshield wiper service. Windshield wiper blades should be inspected periodically. If
they are hardened, cut, or split, replace them.
With electrical problems in a wiper system, refer to the service manual and its wiring
diagram of the circuit. First, check the fuses and electrical connections. If they are good,
use a test light to check for power to the wiper motor.
If power is being fed to the wiper, the motor or transmission may be at fault. Before
replacing the motor or transmission gears, make sure the motor is properly grounded. If
power is not reaching the wiper motor, check the wiper switch and circuit connections
for openings.
If the windshield washer does not work, check the fuse and connections. Use a test light
to check for power going to the motor. If the test light does not glow, the wiper switch
may be bad.
When working on a windshield wiper system, always follow the exact recommendations
given by the manufacturer, as systems and procedures vary with each vehicle.
Normally, the wiper motor must be replaced as a unit. The transmission gears are
usually the only serviceable part in the assembly.
11.6.2 Windshield Washer
A windshield washer consists of a solvent reservoir, pump, rubber hoses, connections,
and washer nozzles. The solvent reservoir, located in the engine compartment, holds a
supply of water and solvent. When the washer switch or button is activated, the wiper
motor and washer pump turn on. Solvent is forced out of the reservoir and onto the
windshield.
There are two common types of pumps used with windshield washer systems: a rotary
pump and a bellows (diaphragm) pump. Most new vehicles use a rotary pump mounted
in the solvent reservoir. A tiny electric motor spins an impeller, which forces the washer
solution onto the windshield. A bellows pump is normally mounted on and powered by
the wiper motor.
Windshield washer service. Many washer problems are caused by restrictions in the
fluid lines or nozzles. To check for restrictions, remove the hose from the pump and
operate the system. If the pump ejects a stream of fluid, then the fault is in the delivery
system. The exact location of the restriction can be found by reconnecting the fluid line
to the pump and disconnecting the line at another location. If the fluid still streams out,
the problem is after that new disconnect. If the fluid does not flow out, the problem is
before the hose was disconnected. Repeat this process until the problem is found.
NAVEDTRA 14050A 6-62

If the pump does not spray out a
steady stream of fluid, the problem
is in the pump circuit. It should be
tested in the same way as any
other electrical circuit. Make sure it
gets power from the switch when it
should, then check the ground. If
the power to the pump is good and
there is a good ground, the
problem is the pump. Pumps are
not rebuilt or repaired; they must
be replaced.
11.6.3 Power Windows
A power window uses a control
switch, reversible electric motor,
circuit breaker, fuse, and related
wiring to operate the door
windows.
A small electric power window
motor is located inside each door
to operate the window regulator
(up-down mechanism for the
glass). The motors have a
Figure6-64 - Schematicsimplepower
windowcircuitforapassenger-sidewindow.
gearbox, or transmission (usually worm and ring gear), that changes the rotating motion
of the motor armature into a partial rotation of a larger gear. This action pushes the
window open or closed.
A circuit breaker protects the window motor from overheating damage. The breaker can
open if the switch is held in one position too long. The circuit breaker can be located
inside the motor or elsewhere in the circuit. A simple power window circuit for a
passenger-side power window is shown in Figure 6-64.
Some power windows will stop or reverse direction if an obstruction resists window
closing. In some of these systems, a magnetic trigger wheel is mounted on the motor's
armature shaft. As the trigger wheel turns, it creates a signal in a magnetic or Hall-effect
sensor in the motor assembly. If the sensor outputs a slower-than-normal signal, the
power windows ECM will cut voltage or reverse polarity of the voltage going to the
window motor. This stops the window or lowers it to prevent damage to objects or injury
to people who accidentally put their hands, head, or arms into the path of the window as
it closes.
Power window service. When none of the power windows work, you first check the
fuse or circuit breaker for the whole system. If only one of the windows is inoperative,
use a test light to check for power to its switches.
If you hear a humming sound when a window switch is pressed, the motor gearbox may
have stripped gear teeth. The plastic gears in the window motor gearbox can strip after
prolonged service. The motor will spin, but movement will not be transferred to the
window. If the motor or the switches are found to be bad, they should be replaced.
With hard-to-find problems, refer to the service manual wiring diagram for the power
windows, which will show all the components that could affect power window operation
and help with troubleshooting.
NAVEDTRA 14050A 6-63

Summary
This chapter has presented information and procedures in troubleshooting electrical
systems. You covered the alternator and its components and function, along with
rectifiers, voltage regulators, and troubleshooting procedures.
The succeeding topics encompassed troubleshooting the cranking system with
emphasis on the various tests, the ignition system and its components and subsystems,
lighting systems, and electrical accessories.
Electric and electronic devices can be found almost everywhere on an automobile,
truck, power generation equipment, and construction equipment. These components
have even replaced some mechanical devices. They are more efficient, compact, and
lighter.
Troubleshooting equipment takes complex diagnostic procedures, much service
literature, and specialized equipment. It is uncommon for the mechanic to get through
even one day without referring to a service manual or technical literature.
Specialized tools, test equipment, and other diagnostic equipment, as well as service
manuals and technical literature, are rapidly becoming a necessary requirement.
NAVEDTRA 14050A 6-64

Review Questions (Select the Correct Response)
1. The voltage regulator maintains an alternator output of how many volts?
A. 10 to 12
B. 12 to 14
C. 13 to 15
D. 14 to 16
2. Diodes, heat sink, and electrical terminal make up what assembly?
A. rotor
B. rectifier
C. brush
D. stator
3. (True or False) The stator is a rotating set of windings mounted between the end
frames.
A. True
B. False
4. There are commonly two types of bearings used in an alternator, one being ball
type. What is the other type of bearings sometimes used?
A. roller thrust
B. roller
C. friction
D. needle
5. The text lists three types of alternator belts. Which of the following is not an
alternator belt?
A. ribbed V-belt
B. conventional V-belt
C. ribbed belt
D. cogged V-belt
6. Which component of the alternator feeds the diode trio?
A. stator
B. rotor
C. rectifier
D. diode feeder
NAVEDTRA 14050A 6-65

7. When a diode is connected to voltage source where the current passes through
the diode, the diode is said to be what?
A. Reverse biased
B. Biased
C. Forward biased
D. An insulator
8. There are four basic types of voltage regulators. Where might the electronic
regulator be mounted?
A. Inside the alternator
B. Away from alternator in engine compartment
C. On the rear of the alternator
D. On the front of the alternator
9. The electronic voltage regulator increases alternator output by doing what?
A. Allowing more current into the rotor windings
B. Preventing more current into the rotor windings
C. Allowing less current into the rotor windings
D. Allowing more current into the stator windings
10. Field circuit modulation refers to how the can cycle the rotor field
current on and off to control charging system output.
A. stator
B. diode trio
C. voltage regulator
D. rectifier bridge
11. (True or False) It is not necessary to disconnect the battery before moving any
charging system components if the ignition is off.
A. True
B. False
12. While testing a 12-volt system, the voltmeter reads 15 volts. What is the reason
for this high output?
A. Blown fuse
B. Shorted field wire
C. Grounded field
D. Current limiter relay of the regulator
NAVEDTRA 14050A 6-66

13. Circuit resistance tests are used to locate wiring problems in a charging system
by testing voltage between which components?
A. Alternator output terminal and the negative battery post
B. Alternator output terminal and positive battery terminal or negative battery
terminal and alternator housing.
C. Alternator housing and positive battery terminal
D. Alternator input terminal and negative battery terminal or positive battery
terminal and alternator housing
14. When performing a regulator ground circuit resistance test, a voltmeter reading
exceeding how many volts indicates a possible damaged ground strap or loose
mountings?
A. 0.01
B.
0.10
C.
1.00
D.
1.10
15. When using an ohmmeter to test diodes, what must you do?
A. Connect the diodes with a piece of wire.
B. Remove the diodes from the alternator.
C. Disconnect the stator windings.
D. Unsolder the diodes and isolate them.
16. When testing a diode with an ohmmeter and it reads high resistance in one
direction and low resistance in the other, what does this reading tell you?
A. The diode is good.
B. The diode is shorted.
C. The diode is open.
D. Replace the diode.
17. A weak diode will produce what type of pattern on an analyzer screen?
A. A high or low peak every sixth pulse
B. A flat signal each sixth pulse
C. A low ripple pattern
D. A steep peak every sixth pulse
18. On a vehicle equipped with a 24-volt series parallel starting system, what
minimum voltmeter reading is considered normal for a cranking voltage test?
A. 12 volts
B. 14 volts
C. 16 volts
D. 18 volts
NAVEDTRA 14050A 6-67

19. While conducting a starter insulated circuit test, what maximum allowed voltage
drop is the norm across the length of a cable?
A.
0.01
B.
0.10
C.
1.00
D.
1.10
20. During a starter ground circuit resistance test, the measured voltage loss
exceeds 0.2 volt or the loss given by the manufacturer's specifications. This loss
can result from which of the following problems?
A. Loose starter bolt
B. Poor battery ground terminal post connector
C. Damaged undersized ground system wire
D. Each of the above
21. What component of the ignition system boosts battery voltage to a much as
60,000 volts?
A. Alternator coil
B. Ignition switch
C. Ignition coil
D. Battery booster
22. (True or False) An electronic ignition is more dependable than a contact point
because there are no mechanical breakers to wear or burn.
A. True
B. False
23. A solid-state chip or module that produces an electrical signal when triggered by
a slotted wheel is called what?
A. Hall-effect pickup
B. Trigger wheel
C. Permanent magnet
D. Pickup coil
24. In the distributorless ignition system, what component consists of two or more
ignition coils?
A. power distribution module
B. distributorless coil module
C. ignition module
D. electronic coil module
NAVEDTRA 14050A 6-68

25. The following are all advantages of distributorless ignition system over ignition
systems with a distributor except:
A. No mechanical weights
B. No vacuum advance diaphragm
C. More moving parts to wear and malfunction
D. No rotor or distributor cap
26. What component is eliminated with a direct ignition system?
A. coils
B. spark plugs
C. ignition wires
D. spark plug wires
27. In a computerized ignition system, heat will upset the operation of the electronic
components in what unit?
A. Power distribution module
B. Ignition control module
C. Electronic power module
D. Computer module
28. In the electronic ignition system, what test compares actual resistance or voltage
output?
A. Magnetic pickup coil
B. Ignition coil
C. Electronic ignition resistance
D. Magnetic voltage
29. When conducting a Hall-effect sensor with an oscilloscope, how should the
waveform appear?
A. Switch slowly, angled sides, top square reaching reference voltage, and
bottom should reach zero
B. Switch rapidly, sloped sides, top rounded reaching reference voltage, and
bottom should reach zero
C. Switch rapidly, vertical sides, top square reaching reference voltage, and
bottom should reach zero
D. Switch intermittently, vertical sides, top arched reaching reference
voltage, and bottom should reach zero
30. (True or False) In a direct ignition coil test, you will measure both primary and
secondary winding resistance.
A. True
B. False
NAVEDTRA 14050A 6-69

31. The halogen lamp typically consists of a bulb filled with what type of vapor?
A. halogen
B. oxygen
C. iodine
D. fluoride
32. How would you identify a type 1 sealed-beam headlight?
A. Both low and high beam and three terminals
B. Both low and high beam and two electrical terminals
C. "H" molded on the lens
D. High beam only and two electrical terminals
33. If one bulb is not working and you determined it is not burned out, what should
you check for before replacing the bulb?
A. voltage at socket
B. ignition switch
C. headlight control module
D. amperage
34. Most fuses are designed to maintain what percent of overload current
indefinitely?
A.
105
B.
110
C.
115
D.
None of the above
35. (True or False) Blade fuses come in three sizes, sometimes referred to by their
trade names. They are Mini-fuse, auto-fuse, and Maxi-fuse.
A. True
B. False
36. Trucks will have large, bolt-in type fuses that are commonly used to protect main
battery power feed cable that supplies what?
A. The trailer electrical system
B. The engine electrical system
C. The headlights and taillights
D. The cab electrical system
37. The special insulation material used in a fusible link has what characteristics?
A. Melts off and is flammable
B. Does not melt off nor support flame
C. Does not melt off but is flammable
D. None of the above
NAVEDTRA 14050A 6-70

38. A Type I circuit breaker has which characteristic?
A. Resets automatically
B. Resets automatically after cause is relinquished
C. Manually resets
D. Resetsautomatically with operator intervention
39. The turn signal flasher unit operates by the heating and cooling of which
temperature-sensitive component?
A. Bimetallic strip
B. Metallic connector
C. Copper wire
D. Bimetallic filament
40. Which type of flasher typically contains a power metal-oxide-semiconductor field-
effect transistor?
A. Hybrid
B. Solid-state
C. Bimetallic
D. Electronic
41. The brake light switch is normally mounted on the brake pedal, but can also be
mounted at what other location?
A. Master cylinder
B. Brake line
C. Steering column
D. Both A and B
42. The color of wiring insulation is standardized. What color is the wire for the STOP
lamps and antilock devices?
A. Red
B. Green
C. Brown
D. Blue
43. The tractor normally provides the circuit protection for trailer wiring or can have a
separate component mounted on the tractor. What is the additional component
with fuses and relays for trailers called?
A. Electrical relay system
B. Power delivery box
C. Power distribution module
D. Tractor/trailer power transmitter
NAVEDTRA 14050A 6-71

44. (True or False) The horn system uses a coil-operated diaphragm to produce
audible sound.
A. True
B. False
45. The metal core that is attached by magnetic field of coil windings is what part of a
horn?
A. Outlet
B. Plunger
C. Contacts
D. Horn coil
46. What should the amp reading generally be when troubleshooting a horn?
A.
2-3
B.
3-4
C.
4-5
D.
5-6
47. After making all the required checks on the windshield washer and determining
that the pump is bad, what is the next step ?
A. Rebuild the pump
B. Replace the pump
C. Repair the pump
D. Tap on the pump
48. When troubleshooting an inoperative power window, you can hear a humming
noise where the motor is spinning, but there is no movement of the window.
What may be the problem?
A. Stripped plastic gears
B. Stripped window cam
C. Bent tracking system
D. Stripped plastic rotor
NAVEDTRA 14050A 6-72