1988 JEEP CHEROKEE radio

be obtained. During high speeds "on" time may be 10 percent and "off"
time 90 percent. During low speeds with high electrical loads, "on"
time may be 90 percent and "off" time 10 percent.
SI SERIES
A rectifier bridge, connected to stator windings, contains 6
diodes (3 positive and 3 negative) molded into an assembly. This
rectifier bridge changes stator AC voltage into DC voltage, which
appears at output terminal.
Alternator field current is supplied through a diode trio
which is also connected to stator windings. A capacitor is mounted to
end frame, protecting rectifier bridge and diodes from high voltage
and suppressing radio interference noise.
TROUBLE SHOOTING
NOTE: See the TROUBLE SHOOTING - BASIC PROCEDURES article
in the GENERAL TROUBLE SHOOTING section.
TESTING
PRELIMINARY INFORMATION
NOTE: Before making electrical checks, visually inspect all
terminals for clean, tight connections. Check alternator
mounting bolts and drive belt tension. Battery must be in
good condition to test charging system.
TESTING (ON-VEHICLE)
CS SERIES
Over/Undercharged Battery (W/ STandard Instruments)
1) If an overcharging condition is suspected, run engine at a
moderate speed. Connect a voltmeter across battery terminals. If
voltmeter indicates more than 16 volts, replace alternator.
2) If an undercharging condition is suspected, disconnect
2
wire connector from alternator. Turn ignition on with engine off.
Connect a voltmeter between terminal "L" in wiring harness and ground.
Record reading.
3) If terminal "I" is used, connect voltmeter between
terminal "I" and ground. Record reading. If voltmeter reads battery
voltage, circuits are okay. If voltmeter reads zero, this indicates an
open circuit between terminal checked and battery. Repair as
necessary.
Overcharged Battery (W/ Gauges)
If an overcharging condition is suspected, run engine at a
moderate speed. Connect a voltmeter across battery terminals. If
voltmeter indicates more than 16 volts, replace alternator.
Alternator Output Test (W/ Standard Instruments Or Gauges)
1) Run engine at moderate speed, all electrical accessories
off. Measure voltage across battery, if above 16 volts, replace
alternator.
2) Connect an ammeter in circuit at "BAT" terminal of
alternator. Turn on all available accessories. Connect a battery load
tester across battery. Operate engine at 2000 RPM and adjust battery
load tester as required to obtain maximum current output while

switch.
Fuse C Taped to engine wiring
harness, by alternator.
Fuse D Taped to engine wiring
harness, near power steering
switch.
Cruise Control Under left side of dash, near
brake pedal.
Radio Under center of dash, behind
radio.









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CONTROL UNITS









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Component Component Location
Audio Alarm Module On side of fuse block.
Cruise Control Regulator Module Under dash, above brake pedal.
Elect. Control Unit (ECU) Under dash, above accelerator
pedal.

1 - 25 Amp
Rear Washer/Wiper.
2 - 15 Amp
Radio, Cigarette Lighter.
3 - 25 Amp
Blower Motor.
4 - 20 Amp
Turn Signal, Back-Up Lights, Rear Window Defogger Relay.
5 - 10 Amp
Dome Light, Courtesy Lights, Glove Box Light, Cargo Light,
Radio Memory, Power Mirrors, Teltak Connector.
6 - 15 Amp
Hazard Warning System, Stoplights.
7 - 10 Amp
Parking Lights, Headlight Warning Chime/Buzzer, Instrument
Panel Light Dimmer.
8 - 7.5 Amp
Gauges, Instrument Cluster, Seat Belt Warning, Headlight
Delay, Chime Module, Overhead Console.
9 - 5 Amp
Instrument Panel Illumination.
10 - 25 Amp
Rear Window Defogger.
11 - 30 Amp (Circuit Breaker)
Power Door Locks, Power Seats, Trailer Towing Wiring Harness.
12 - 10 Amp
ETR Radio, Power Antenna.
13 - Not Used (1984-87); 7.5 Amp (1988)
Transmission Control Unit.
14 - 25 Amp
Headlight Delay, Horns, Security Alarm.
15 - 5.5 Amp (Circuit Breaker)
Front Wiper.
16 - 30 Amp (Circuit Breaker)
Power Windows.
17 - 10 Amp
Clock, Security Alarm (Ign).
CAUTIONS & WARNINGS
REPLACING BLOWN FUSES
Before replacing a blown fuse, remove ignition key, turn off
all lights and accessories to avoid damaging the electrical system. Be
sure to use fuse with the correct indicated amperage rating. The use
of an incorrect amperage rating fuse may result in a dangerous

Fig. 2: Typical Heater & Defroster Components
Courtesy of Chrysler Motors.
BLOWER MOTOR R & I
NOTE: On Cherokee and Comanche, blower motor and fan are removed
from engine compartment.
Removal & Installation
1) Remove heater core housing assembly. On all models, remove
blower motor electrical connectors. Detach screws retaining blower
motor assembly to heater housing. Remove blower motor and fan
assembly. On Cherokee and Comanche, detach fan retaining clip from fan
hub, if necessary. Remove fan from motor shaft.
2) To install, reverse removal procedure. If removed, ensure
ears of retaining clip are over flat surface on motor shaft. Check
blower motor and heater operation.
CONTROL PANEL R & I
Removal & Installation
1) Disconnect battery ground. On Cherokee, remove lower
instrument panel. On all models, remove instrument panel bezel. On
Cherokee, remove clock and radio (if equipped).
2) On all models, remove heater control panel attaching
screws. Pull out control panel and disconnect vacuum hoses, wires and
cables. Note locations for reassembly reference. Remove control panel.
To install, reverse removal procedure.
CONTROL CABLES R & I
REMOVAL (CHEROKEE & COMANCHE)
Remove control panel. Detach cable from heater control panel.

Removal & Installation
Using care, disconnect the spark plug and coil wire boots and
wires. Twist the boot one half turn and pull on the boot to disconnect
the wire.
When replacing the spark plug and coil wires, carefully route
the wires correctly and secure them in their proper channels
retainers.
Failure to route the wires properly can cause the radio to
reproduce ignition noise, cross ignition of the plugs, or can short
circuit the wires to ground.
OVERHAUL
STATOR REPLACEMENT
Disassembly
1) Remove the distributor as specified in DISTRIBUTOR under
REMOVAL & INSTALLATION above in this article.
2) Remove the distributor rotor.
3) Position the distributor in a vise.
4) Remove the distributor gear from the shaft using a small
punch and a hammer to drive out the retaining roll pin. See Fig. 29.
5) Remove the distributor shaft from the distributor housing.
6) Remove the stator retaining screw.
NOTE: Mark the location of the stator position for reassembly
reference.
Fig. 29: Removing Distributor Gear Retaining Roll Pin
Courtesy of Chrysler Motors.
7) Remove stator harness by pushing the grommet through the
distributor housing. Remove stator assembly. See Fig. 30.

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IG NIT IO N S YSTE M - 4 .0 L W /H EI/E ST/E SC ( D ELC O -R EM Y)

1 988 J e ep C hero ke e
Distributors & Ignition Systems
HEI, HEI/EST & HEI/EST/ESC IGNITION SYSTEM
Jeep 4.0L
DESCRIPTION
HIGH ENERGY IGNITION (HEI)
The Delco-Remy High Energy Ignition system is a self-
contained unit. It consists of ignition coil, spark plugs, distributor
assembly and primary and secondary wiring. The distributor housing
contains an electronic control module, pick-up coil, pole piece, timer
core, rotor, capacitor for radio noise suppression and timing advance
mechanisms. Most applications house the ignition coil assembly within
the distributor cap. See Fig. 1.
Fig. 1: Delco-Remy HEI System Circuit Diagram
Courtesy of General Motors Corp.
HEI WITH ELECTRONIC SPARK TIMING (EST)

The capacitor is used for radio noise supression. Set
ohmmeter at x1000 scale. Disconnect capacitor. Touch ohmmeter leads to
capacitor terminal and ground. Slight needle movement will occur
rapidly and return to infinity. A continuous reading other than
infinity indicates defective capacitor.
COMPONENT TESTING (HEI WITH EST)
COIL RESISTANCE CHECK
Externally Mounted Ignition Coil (Sealed Module Connector
Distributor)
Remove coil connectors and secondary coil wire. In test "A",
use high ohmmeter scale. See Fig. 7. If continuity is present, replace
coil. In test "B", use low ohmmeter scale. Reading should be very low
or near zero. If not, replace coil. In test "C", use high ohmmeter
scale. If there is no continuity, replace coil.
Fig. 7: Testing Ignition Coil Resistance, External coil system shown.
Courtesy of General Motors Corp.
Integrally Mounted Ignition Coil
1) Turn ignition off. Remove the distributor cap and coil

1 - 25 Amp
Rear Washer/Wiper
2 - 15 Amp
Radio, Cigarette Lighter
3 - 25 Amp
Blower Motor
4 - 20 Amp
Turn Signal, Back-Up Lights, Rear Window Defogger Relay
5 - 10 Amp
Dome Light, Courtesy Lights, Glove Box Light, Cargo Light,
Radio Memory, Power Mirrors, Teltak Connector
6 - 15 Amp
Hazard Warning System, Stoplights
7 - 10 Amp
Parking Lights, Headlight Warning Chime/Buzzer, Instrument
Panel Light Dimmer
8 - 7.5 Amp
Gauges, Instrument Cluster, Seat Belt Warning,
Headlight Delay, Chime Module, Overhead Console
9 - 5 Amp
Instrument Panel Illumination
10 - 25 Amp
Rear Window Defogger
11 - 30 Amp (Circuit Breaker)
Power Door Locks, Power Seats, Trailer Towing Wiring Harness
12 - 10 Amp
ETR Radio, Power Antenna
13 - Not Used (1984-87)
7.5 Amp (1988)
Transmission Control Unit
14 - 25 Amp
Headlight Delay, Horns, Security Alarm
15 - 5.5 Amp (Circuit Breaker)
Front Wiper
16 - 30 Amp (Circuit Breaker)
Power Windows
17 - 10 Amp
Clock, Security Alarm (IGN)