1988 JEEP CHEROKEE heater
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Fig. 5: Heater Wiring Diagram (Comanche Gas)
Fig. 6: Heater Wiring Diagram (Wrangler)
Page 871 of 1378
housing with 2 shoulder bolts. Tighten the engine speed sensor
shoulder bolts.
2) Connect the engine speed sensor wire connector.
ELECTRONIC CONTROL UNIT (ECU)
Removal
NOTE: The ECU is located below the instrument panel, between
the steering column and the A/C-Heater housing. See
Fig. 22. Three screws mount the ECU to a bracket.
1) Disconnect the negative battery cable.
2) Remove the 3 ECU attaching screws. See Fig. 23.
3) Disconnect the ECU wiring harness connector.
4) Remove the ECU.
Fig. 22: Location of ECU
Courtesy of Chrysler Motors.
Page 1188 of 1378
Fig. 7: Brakes, Steering, & Suspension
Fig. 8: Air Conditioning, Heater & Ventilation
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![JEEP CHEROKEE 1988 Service Repair Manual Fires With Key Flywheel runout contributes
released. Engine to the intermittent nature
Fires and Cranks
Normally
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\](/manual-img/16/57037/w960_57037-1229.png "JEEP CHEROKEE 1988 Service Repair Manual Fires With Key Flywheel runout contributes
released. Engine to the intermittent nature
Fires and Cranks
Normally
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Fires With Key Flywheel runout contributes
released. Engine to the intermittent nature
Fires and Cranks
Normally
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AIR CONDITIONING & HEAT
AIR CONDITIONING TROUBLE SHOOTING
WARNING: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing.
BASIC AIR CONDITIONING TROUBLE SHOOTING CHART
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CONDITION POSSIBLE CAUSE \
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Compressor Not Working
Compressor clutch circuit open.
Compressor clutch coil inoperative.
Poor clutch ground connection.
Fan belts loose.
Thermostatic switch inoperative.
Thermostatic switch not adjusted.
Ambient temperature switch open.
Superheat fuse blown. \
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Excessive Noise or Vibration
Missing or loose mounting bolts.
Bad idler pulley bearings.
Fan belts not tightened correctly.
Compressor clutch contacting body.
Excessive system pressure.
Compressor oil level low.
Damaged clutch bearings.
Damaged reed valves.
Damaged compressor. \
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Insufficient or No Cooling;
Compressor Working
Expansion valve inoperative.
Heater control valve stuck open.
Low system pressure.
Blocked condenser fins.
Blocked evaporator fins.
Vacuum system leak.
Vacuum motors inoperative.
Control cables improperly adjusted.
Restricted air inlet.
Mode doors binding.
Blower motor inoperative.
Temperature above system capacity. \
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HEATER SYSTEM TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
Page 1231 of 1378
problem symptoms. For model-specific Trouble Shooting,
refer to DIAGNOSTIC, or TESTING articles available in the
section(s) you are accessing.
BASIC HEATER SYSTEM TROUBLE SHOOTING CHART
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CONDITION POSSIBLE CAUSE \
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Insufficient, Erratic,
or No Heat
Low Coolant Level
Incorrect thermostat.
Restricted coolant flow through
heater core.
Heater hoses plugged.
Misadjusted control cable.
Sticking heater control valve.
Vacuum hose leaking.
Vacuum hose blocked.
Vacuum motors inoperative.
Blocked air inlet.
Inoperative heater blower motor.
Oil residue on heater core fins.
Dirt on heater core fins. \
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Too Much Heat
Improperly adjusted cables.
Sticking heater control valve.
No vacuum to heater control valve.
Temperature door stuck open. \
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Air Flow Changes During
Acceleration
Vacuum system leak.
Bad check valve or reservoir. \
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Air From Defroster At All
Times
Vacuum system leak.
Improperly adjusted control cables.
Inoperative vacuum motor. \
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Blower Does Not Operate
Correctly
Blown fuse.
Blower motor windings open.
Resistors burned out.
Motor ground connection loose.
Wiring harness connections loose.
Blower motor switch inoperative.
Blower relay inoperative.
Fan binding or foreign object
in housing.
Fan blades broken or bent. \
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BRAKES
BRAKE SYSTEM TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing.
Page 1235 of 1378
Water Pump Malfunction Replace Water Pump
Fan Clutch Malfunction Replace Fan Clutch
Retarded Ignition Timing Reset Ignition Timing
Cooling Fan Malfunction Test Cooling Fan/
Circuit
Cooling Fan Motor
Malfunction Test Fan Motor
Cooling Fan Relay
Malfunction Test Fan Relay
Faulty Radiator Cap Replace Radiator Cap
Broken/Slipping Fan Belt Replace Fan Belt
Restricted Exhaust Repair Exhaust System
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Corrosion Impurities In Coolant Clean/Flush System \
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Coolant Leakage Damaged hose Replace Hose
Leaky Water Pump Replace Water Pump
Damaged Radiator Seam Replace/Repair Radiator
Leaky Thermostat Cover Replace Thermostat
Cover
Cylinder Head Problem Check Head/Head Gasket
Leaky Freeze Plugs Replace Freeze Plugs
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Recovery System Inoperative
Loose and/or Defective
Radiator Cap Replace Radiator Cap
Overflow Tube Clogged
and/or Leaking Repair Tube
Recovery Bottle Vent
Restricted Clean Vent
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No Heater Core Flow
Collapsed Heater Hose Replace Heater Hose
Plugged Heater Core Clean/Replace Heater
Core
Faulty Heater Valve Replace Heater Valve
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GASOLINE ENGINE - MECHANICAL TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
Page 1365 of 1378
Fig. 8: Diode (Light Emitting)
Fig. 9: Defogger Grid
Fig. 10: Fuse
Fig. 11: Fusible Link
Fig. 12: Ground
Fig. 13: Glow Plug Resistor (In-Line) or Mirror Heater