1988 JEEP CHEROKEE ignition

30-50 ohms. Resistance between terminals No. 4 and ground, and
terminal No. 12 and ground should be infinite (open).
WRANGLER CRUISE CONTROL TESTING









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Conditions Lights "ON"
Control Switch "ON" & Set Switch Depressed .................. No. 1
Control Switch "ON" ......................................... No. 2
Ignition "ON" & Brake or Clutch Pedal Depressed ..... No. 3 & No. 4
Cruise Control & Resume/Accel "ON" .................. No. 5 & No. 6
Cruise & Resume/Accel "ON" & Engine Running (1) ..... No. 5 & No. 6
( 1) - Servo will pull throttle wide open. Keep RPM at a safe level by
releasing cruise control switch.









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Except Wrangler
Use 12-volt test light to test control switch continuity.
Connect test light to wires as indicated in CONTROL SWITCH CONTINUITY
TEST CHART. See Figs. 3 or 4.
Fig. 3: Cherokee, Comanche & Wagoneer Control Switch Continuity Test
Chart
Courtesy of Chrysler Motors.

Fig. 4: Grand Wagoneer Control Switch Continuity Test Chart
Courtesy of Chrysler Motor.
CORRECT POWER SOURCE
Cherokee, Comanche & Wagoneer
1) With ignition switch and control switch "OFF", all test
lights should be off. If any light is on, check Brown (7) wire is not
connected directly to source of voltage.
2) Check for bad control switch. With ignition switch in
"OFF" position, and control switch "ON". Light No. 2 should be on and
lights No. 1, 3, 4, 5 and 6 should be off.
3) If light No. 2 is off, check speed sensor continuity,
check speed sensor terminals to Gray and Drk. Blue wires, and check
that terminals No. 2, 3, 5 and 7 (Gray, Drk. Blue and Lt. Green wires
are not grounded).
Grand Wagoneer

With ignition and control switches in "OFF" position, test
lights should be off. If one or more lights are on, remove Brown (5)
wire at control module connector and check for direct source of
voltage or repair defective control switch.
SYSTEM ELECTRICAL CONTINUITY
Cherokee, Comanche & Wagoneer
1) With ignition and control switches in "ON" position,
lights No. 2, 3 and 4 should be on. Lights No. 1, 5 and 6 should be
off. If light No. 2 is off, check speed sensor continuity, check speed
sensor terminals to Gray and Drk. Blue wires, and check terminals No.
2, 3, 5 and 7 (Gray, Drk. Blue and Lt. Green wires are not grounded).
2) If light No. 3 is off, check brake light switch and all
Brown, Lt. Blue and Lt. Green wire connections. If light No. 4 is off,
check terminals No. 2 and No. 11 at control module connector. Check
continuity of throttle position feedback rheostat of servo.
Grand Wagoneer
1) With ignition and control switches in "ON" position,
lights No. 1, 2, 3, and 4 should be on. Lights No. 5 and 6 should be
off. If light No. 1 is off, check for blown fuse in brake light switch
to control switch circuit. Check Red, Brown and Green wires at control
switch for continuity to switch. Check Drk. Green wire (14) at control\
module connector for continuity to control module.
2) If light No. 2 is off, check speed sensor for correct
output voltage. Check Gray and Drk. Blue wire at speed sensor
connector for continuity to control module connector. Check terminals
No. 2, 3, 5 and 7 at control module connector for proper connection to
wires.
3) If light No. 3 is off, check brake and clutch switch
adjustment. If light No. 4 is off, check for defective connection at
terminals No. 2 and 11 on control module connector. Check operation of
throttle position feedback rheostat on servo.
COAST CONTINUITY TEST
Cherokee, Comanche & Wagoneer
1) With ignition and control switches in "ON" position,
depress and hold "SET/COAST" button. Lights No. 1, 2, 3 and 4 should
be on. Lights No. 5 and 6 should be off. If light No. 1 is off, check
voltage from brake light switch, check 4-amp in-line fuse of Pink
wire, and check Pink, Brown and Drk. Green wires at control switch
connector and Drk. Green (14) wire at control module connector for
good connections.
2) If light No. 2 is off, check speed sensor continuity,
check speed sensor terminals to Gray and Drk. Blue wires, and check
terminals No. 2, 3, 5 and 7 (Gray, Drk. Blue and Lt. Green wires) for
ground.
3) If light No. 3 is off, check brake light switch, check all
Brown, Lt. Blue and Lt. Green wire connections. If light No. 4 is off,
check terminals No. 2 and 11 at control module connector, and check
continuity of throttle position feedback rheostat of servo.
SERVO CHARGE VALVE SOLENOID CONTINUITY
CAUTION: If engine is running, servo will move throttle to wide open
position.
Grand Wagoneer
1) With ignition and control switches in "ON" position,
depress and hold "SET/COAST" button. Lights No. 2, 3, 4, 5 and 6
should be on. Light No. 1 should be off. Light No. 4 will dim when

servo moves throttle to wide open position with engine operating.
2) If light No. 2 is off, check speed sensor for correct
output voltage. Check Gray and Drk. Blue wire at speed sensor
connector for continuity to control module connector. Check terminals
No. 2, 3, 5 and 7 at control module connector for proper connection to
wires.
3) If light No. 3 is off, check brake and clutch switch
adjustment. If light No. 4 is off, check for defective connection at
terminals No. 2 and 11 on control module connector. Check operation of
throttle position feedback rheostat on servo.
4) If light No. 5 is off, check for defective connections at
terminals No. 4 and 12 on control module connector. If necessary,
replace defective servo. If light No. 6 is off, check for defective
connection at terminals No. 6 and 12 on control module connector. If
necessary, replace defective servo.
5) If all lights are off after depressing set/coast speed
switch, check for blown fuse. Check for short circuits in Red, Pink
and Brown wire circuits at control switch. If necessary, replace
defective servo.
SYSTEM DISENGAGEMENT WITH BRAKE PEDAL DEPRESSED
Cherokee, Comanche & Wagoneer
1) With ignition and control switches in "ON" position and
brake pedal depressed, lights No. 2 and 4 should be on. Lights No. 1,
3, 5 and 6 should be off. Light No. 3 should be on when brake pedal is
released.
2) If light No. 2 is off, check speed sensor continuity,
check speed sensor terminals to Gray and Drk. Blue wires, and check
terminals No. 2, 3, 5 and 7 (Gray, Drk. Blue and Lt. Green) for
ground.
3) If light No. 4 is off, check terminals No. 2 and 11 at
control module connector, and check continuity of throttle position
feedback rheostat of servo.
Grand Wagoneer
1) With ignition and control switches in "ON" position and
brake pedal depressed, lights No. 1, 2 and 4 should be on. Lights No.
3, 5 and 6 should be off. Light No. 3 should be on when brake pedal is
released.
2) If light No. 1 is off, check for blown fuse in brake light
switch to control switch circuit. Check Red, Brown and Green wires at
control switch connector for continuity to switch. Check Drk. Green
wire (14) at control module connector for continuity to control
module.
3) If light No. 2 is off, check speed sensor for correct
output voltage. Check Gray and Drk. Blue wire at speed sensor
connector for continuity to control module connector. Check terminals
No. 2, 3, 5 and 7 at control module connector for proper connection to
wires.
4) If light No. 4 is off, check for defective connection at
terminals No. 2 and 11 on control module connector. Check operation of
throttle position feedback rheostat on servo. If light No. 3 is off
when brake pedal is released, check brake light switch adjustment.
"RESUME/ACCEL" FUNCTION
CAUTION: If engine is running, servo will move throttle to wide open
position.
Cherokee, Comanche & Wagoneer
1) With ignition and control switches in "ON" position, slide
and hold control switch in "R/A" position. Lights No. 2, 3, 4, 5 and 6

should be on. Light No. 1 should be off. Light No. 4 will dim when
servo moves throttle to wide open position, if engine is running.
2) If light No. 2 is off, check speed sensor terminal
connections to control module through Gray and Drk. Blue wires. Check
terminals No. 2, 3, 5 and 7 (Gray, Drk. Blue and Lt. Green wires) for
ground.
3) If light No. 3 is off, check brake light switch, and check
all Brown, Lt. Blue and Lt. Green wire connections. If light No. 4 is
off, check terminals No. 2 and 11 at control module connector. Check
continuity of throttle position feedback rheostat of servo.
4) If light No. 5 is off, check for bad connection at White
(6) and Orange (12) wire terminals. If necessary, replace defective
servo.
5) If all lights are off after moving control switch to "R/A"
position, check for blown fuse or fuses, and check Red, Pink, Brown or
White wires for shorts. If necessary replace defective servo.
Grand Wagoneer
1) With ignition and control switches in "ON" position, slide
control switch to "R/A" position. All test lights should be on. Light
No. 4 will dim when servo moves throttle to wide open position, if
engine is running.
2) If light No. 1 is off, check for blown fuse in brake light
switch to control switch circuit. Check Red, Brown and Green wires at
control switch for continuity to switch.
3) If light No. 2 is off, check Gray and Drk. Blue wire at
speed sensor connector for continuity to control module connector.
4) If light No. 3 is off, check brake light switch
adjustment. If light No. 4 is off, check for defective connection at
terminals No. 2 and 11 on control module connector. Check operation of
throttle position feedback rheostat on servo.
5) If light No. 5 is off, check for defective connections at
terminals No. 4 and 12 on control module connector. If necessary,
replace defective servo. If light No. 6 is off, check for defective
connection at terminals No. 6 and 12 on control module connector. If
necessary, replace defective servo.
6) If all lights are off after moving control switch to "R/A"
position, check for blown fuse. Check for short circuits in Red, Pink
and Brown wire circuits at control switch. If necessary, replace
defective servo.
SPEED SENSOR TEST
1) Disconnect wire harness connector at speed sensor. Connect
a voltmeter (set on low AC scale) to terminals from speed sensor.
2) Raise front and rear wheels of vehicle off ground and
support vehicle with safety stands. Run engine (wheels spinning
freely) at 30 MPH and note voltage.
3) Voltage should be approximately .9 volts. Increases of .1
volts per each 10 MPH increase in speed should also be noticed. Turn
off engine and stop wheels. Lower vehicle. Connect speed sensor wire
harness.
SERVO TEST
1) With ignition switch in "OFF" position, disconnect servo
wire harness connector. Remove vacuum hose from brake pedal vent valve
nipple on servo. Disconnect servo cable from throttle linkage at
carburetor.
2) Connect an ohmmeter between ground and Red. Ground and
Orange. And Ground and White wire terminals of servo wire harness
connector. See Fig. 5. Observe ohmmeter during each test. An infinite
(open circuit) resistance should be indicated for each wire terminal.

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DEFO GGER - R EA R W IN DO W

1988 J e ep C hero ke e
1988 Defoggers
REAR WINDOW
Jeep: All Models
DESCRIPTION & OPERATION
System consists of 2 vertical bus bars and horizontal rows of
heating elements fused to inside of glass, a control switch, an
indicator light, and timer relay.
The grid feed wire is connected to bus bar on driver's side
of window. Ground bus bar is on right side of vehicle. Timer/relay
receives current from fuse block. A circuit breaker protects defogger
circuit.
NOTE: On some Jeep models, defogger switch and electric tailgate
switch are serviced as an assembly.
TROUBLE SHOOTING
NOTE: Control switch testing is not available for Wrangler models.
1) On Cherokee, Comanche and Wagoneer models, turn ignition
switch to "ON" position. Check for current at "I" and "B" terminals.
See Fig. 1 . If there is no current, check circuit and repair as
necessary. Make sure that switch has a good ground through wire
connected to "G" terminal.
2) With a good ground circuit and ignition switch in "ON"
position, current should be present at "L" terminal. If there is no
current, replace control switch.
Fig. 1: Jeep Control Switch Terminals
3) On Grand Wagoneer models, turn ignition switch to "ON"
position and press defogger switch. Separate wiring harness at
connector under dash. Connect a 12-volt test light from Purple wire to

ground. Test light should light. Turn defogger switch to "OFF"
position. Test light should not light.
GRID
1) Using a voltmeter with a 0-15 volt range, contact bus bar
connecting grid lines on passenger's side of glass with negative lead
of voltmeter. Contact driver's side bus bar with positive lead.
2) Turn ignition and control switches to "ON" position.
Reading should be 10-14 volts. Lower voltage indicates a poor ground.
Attach negative voltmeter lead to ground. Voltage reading should not
vary.
3) Contact negative lead to passenger's side bus bar. Probe
each grid line at midpoint with positive lead. A 6-volt reading
indicates line is good. A zero volt reading indicates a break between
midpoint and driver's side bus bar line.
4) A 10-14 volt reading indicates a break between midpoint
and passenger's side bus bar line. Move positive lead toward break and
voltage will change when break is crossed.
NOTE: On some Jeep models feed wire and ground wires a reversed.
Fig. 2: Grid Continuity Voltage Drop
RELAY
NOTE: No relay testing is available for Wrangler models.

1) On Grand Wagoneer models, attach negative lead of
voltmeter to ground. Probe Red wire at relay with voltmeter positive
lead. Battery voltage should be indicated. If no voltage is indicated,
operate tailgate window.
2) If window operates, wire between relay and window switch
is open. Probe Orange wire at relay with voltmeter positive lead. No
voltage should be indicated. Turn ignition switch to "ON" position.
Voltmeter should indicate voltage. If not, relay is defective or not
receiving voltage from Purple wire.
3) If relay operates properly, it should remain energized for
8 to 12 minutes before opening. If time period is too short or too
long, relay is defective. If relay did not energize, connect a jumper
wire to a 12-volt source in tailgate and probe Purple relay terminal.
4) If relay "clicks", trace Purple wire for open or short. If
relay does not click, check relay ground. If ground is okay, relay
should be replaced.