1995 JEEP YJ Service And Repair Manual

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JEEP YJ 1995 Service And Repair Manual STARTING SYSTEM DIAGNOSIS
8A - 12 BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICSJ

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JEEP YJ 1995 Service And Repair Manual COLD CRANKING TEST
(1) Battery must be fully-charged and load tested
before proceeding. See Battery, in this group.
(2) Connect a suitable volt-ampere tester to the
battery terminals (Fig. 2). Refer t

COLD CRANKING TEST
(1) Battery must be fully-charged and load tested
before proceeding. See Battery, in this group.
(2) Connect a suitable volt-ampere tester to the
battery terminals (Fig. 2). Refer to the operating in-
structions provided with the tester being used.
(3) Fully engage parking brake. Place manual
transmission in NEUTRAL, automatic transmission
in PARK.
(4) Verify that all lamps and accessories are OFF.
(5) Unplug Auto Shut-Down (ASD) relay from
Power Distribution Center (PDC) to prevent engine
from starting. Relay location is shown on underside
of PDC cover.
(6) Rotate and hold the ignition switch in the START
position. Note cranking voltage and amperage.
(a) If voltage reads above 9.6 volts and amperage
draw reads above specifications, see Feed Circuit Tests.
(b) If voltage reads 12.5 volts or greater and am-
perage reads below specifications, see Control Cir-
cuit Tests.
A cold engine will increase starter current
and reduce battery voltage.
FEED CIRCUIT TESTS
The starter feed circuit tests (voltage drop method)
will determine if there is excessive resistance in the
high-amperage circuit. When performing these tests,
it is important that the voltmeter be connected prop-
erly. Connect voltmeter leads to the terminals that
the cable connectors or clamps are attached to, not to
the cable connectors or clamps. For example: When
testing between the battery and solenoid, touch the
voltmeter leads to the battery post and the solenoid
threaded stud.
The following operation will require a voltmeter ac-
curate to 1/10 (0.10) volt. Before performing the tests,
be certain the following procedures are accomplished:
²unplug Auto Shut-Down (ASD) relay from Power
Distribution Center (PDC) to prevent engine from
starting²place transmission in NEUTRAL (manual trans-
mission) or PARK (automatic transmission)
²parking brake is applied
²
battery is fully-charged (see Battery, in this group).
(1) Connect positive lead of voltmeter to battery
negative post. Connect negative lead of voltmeter to
battery negative cable clamp (Fig. 3). Rotate and
hold ignition switch in the START position. Observe
voltmeter. If voltage is detected, correct poor contact
between cable clamp and post.
(2) Connect positive lead of voltmeter to battery
positive post. Connect negative lead of voltmeter to
battery positive cable clamp (Fig. 3). Rotate and hold
ignition switch in the START position. Observe volt-
meter. If voltage is detected, correct poor contact be-
tween cable clamp and post.
(3) Connect voltmeter to measure between the bat-
tery positive post and the starter solenoid battery
stud (Fig. 4). Rotate and hold ignition switch in the
START position. Observe voltmeter. If voltage reads
above 0.2 volt, correct poor contact at battery cable to
solenoid connection. Repeat test. If reading is still
above 0.2 volt, replace battery positive cable.
Fig. 2 Volt-Amps Tester Connections (Typical)
Fig. 3 Test Battery Connection Resistance
Fig. 4 Test Battery Positive Cable Resistance
(Typical)
JBATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS 8A - 13

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JEEP YJ 1995 Service And Repair Manual (4) Connect voltmeter to measure between the bat-
tery negative post and a good clean ground on the
engine block (Fig. 5). Rotate and hold ignition switch
in the START position. Observe voltmeter. If

(4) Connect voltmeter to measure between the bat-
tery negative post and a good clean ground on the
engine block (Fig. 5). Rotate and hold ignition switch
in the START position. Observe voltmeter. If voltage
reads above 0.2 volt, correct poor contact at battery
negative cable attaching point. Repeat test. If read-
ing is still above 0.2 volt, replace battery negative ca-
ble.
(5) Connect positive lead of voltmeter to starter
housing. Connect negative lead of voltmeter to bat-
tery negative terminal (Fig. 6). Rotate and hold igni-
tion switch in the START position. Observe
voltmeter. If voltage reads above 0.2 volt, correct poor
starter to engine ground.
If resistance tests detect no feed circuit problems,
remove the starter and see Solenoid Test in this
group.
CONTROL CIRCUIT TESTS
The starter control circuit consists of:
²starter solenoid
²starter relay
²ignition switch
²park/neutral position switch (automatic transmis-
sion)²wiring harness and connections.
Test procedures for these components are as fol-
lows, and should be followed in the order described.
CAUTION: Before performing any test, unplug Auto
Shut-Down (ASD) relay from Power Distribution
Center (PDC) to prevent engine from starting.
SOLENOID TEST
Refer to Group 8B - Battery/Starter/Generator Ser-
vice for starter removal procedures.
(1) Disconnect solenoid field coil wire from field
coil terminal.
(2) Check for continuity between solenoid terminal
and field coil terminal with a continuity tester. There
should be continuity (Fig. 7).
(3) Check for continuity between solenoid terminal
and solenoid case. There should be continuity (Fig.
8).
(4) If there is continuity, solenoid is good. If there
is no continuity in either test, solenoid has an open
circuit and is faulty. Replace starter assembly.
(5) Connect solenoid field coil wire to field coil ter-
minal.
(6) Install starter as described in Group 8B - Bat-
tery/Starter/Generator Service.
RELAY TEST
The starter relay is in the Power Distribution Cen-
ter (PDC)(Figs. 9 or 10). Refer to the underside of the
PDC cover for relay location.
Fig. 5 Test Ground Circuit Resistance
Fig. 6 Test Starter Ground (Typical)
Fig. 7 Continuity Test Between Solenoid Terminal
and Field Coil Terminal
Fig. 8 Continuity Test Between Solenoid Terminal
and Solenoid Case
8A - 14 BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICSJ

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JEEP YJ 1995 Service And Repair Manual Remove starter relay from PDC to perform the fol-
lowing tests:
(1) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and

Remove starter relay from PDC to perform the fol-
lowing tests:
(1) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and 30. If OK, go
to next step. If not OK, replace faulty relay.
(2) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 7565 ohms. If OK, go to next
step. If not OK, replace faulty relay.
(3) Connect a battery to terminals 85 and 86.
There should now be continuity between terminals
30 and 87, and no continuity between terminals 87A
and 30. If OK, go to Relay Circuit Test. If not OK,
replace faulty relay.
RELAY CIRCUIT TEST
(1) The common feed terminal (30) is connected to
battery voltage and should be hot at all times. If OK,
go to next step. If not OK, check circuit to fuse (F4
for YJ, F10 for XJ) in Power Distribution Center
(PDC). Repair as required.
(2) The normally closed terminal (87A) is con-
nected to terminal 30 in the de-energized position,
but is not used for this application. Go to next step.
(3) The normally open terminal (87) is connected to
the battery terminal (30) in the energized position.
This terminal supplies battery voltage to the starter
solenoid field coils. There should be continuity be-
tween cavity for relay terminal 87 and the starter so-
lenoid terminal at all times. If OK, go to next step. If
not OK, repair circuit to solenoid as required.
(4) The coil battery terminal (86) is connected to
the electromagnet in the relay. It is energized when
the ignition switch is in the START position. Check
for battery voltage at cavity for relay terminal 86with ignition switch in the START position. If OK, go
to next step. If not OK, refer to Group 8D - Ignition
Systems for testing and service of the ignition switch.
(5) The coil ground terminal (85) is connected to
the electromagnet in the relay. On vehicles with an
automatic transmission, it is grounded through the
park/neutral position switch. On vehicles with a
manual transmission, it is grounded at all times.
Check for continuity to ground at cavity for relay ter-
minal 85. If not OK and vehicle has manual trans-
mission, repair circuit as required. If not OK and
vehicle has automatic transmission, refer to Group
21 - Transmission and Transfer Case for testing and
service of the park/neutral position switch.
Fig. 9 Power Distribution CenterÐXJ
Fig. 10 Power Distribution CenterÐYJ
STARTER RELAY CONNECTIONS
JBATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS 8A - 15

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JEEP YJ 1995 Service And Repair Manual IGNITION SWITCH TEST
Refer to Group 8D - Ignition Systems for testing
and service of this component.
PARK/NEUTRAL POSITION SWITCH TEST
Refer to Group 21 - Transmission and Transfer
Case for testing an

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JEEP YJ 1995 Service And Repair Manual CHARGING SYSTEM
GENERAL INFORMATION
The charging system consists of:
²generator
²voltage regulator circuitry (within PCM)
²ignition switch
²battery
²generator warning lamp or voltmeter (depending

CHARGING SYSTEM
GENERAL INFORMATION
The charging system consists of:
²generator
²voltage regulator circuitry (within PCM)
²ignition switch
²battery
²generator warning lamp or voltmeter (depending
on vehicle equipment)
²wiring harness and connections.
Following is a general description of the major
charging system components. Refer to Group 8W -
Wiring Diagrams for complete circuit descriptions
and diagrams.
The charging system is turned on and off with the
ignition switch. When the ignition switch is turned to
the ON position, battery voltage is applied to the
generator rotor through one of the two field termi-
nals to produce a magnetic field. The generator is
driven by the engine through a serpentine belt and
pulley arrangement.
As the energized rotor begins to rotate within the
generator, the spinning magnetic field induces a cur-
rent into the windings of the stator coil. Once the
generator begins producing sufficient current, it also
provides the current needed to energize the rotor.
The wye (Y) type stator winding connections de-
liver the induced AC current to 3 positive and 3 neg-
ative diodes for rectification. From the diodes,
rectified DC current is delivered to the vehicle elec-
trical system through the generator battery and
ground terminals.
The amount of DC current produced by the gener-
ator is controlled by the generator voltage regulator
(field control) circuitry, contained within the Power-
train Control Module (PCM)(Fig. 1). This circuitry is
connected in series with the second rotor field termi-
nal and ground.
Voltage is regulated by cycling the ground path to
control the strength of the rotor magnetic field. The
generator voltage regulator circuitry monitors system
line voltage and ambient temperature. It then com-
pensates and regulates generator current output ac-
cordingly.
The generator is serviced only as a complete as-
sembly. If the generator fails for any reason, the en-
tire assembly must be replaced. The generator
voltage regulator (field control) circuitry can be ser-
viced only by replacing the entire PCM.
All vehicles are equipped with On-Board Diagnos-
tics (OBD). All OBD-sensed systems, including the
generator voltage regulator (field control) circuitry,
are monitored by the PCM. Each monitored circuit is
assigned a Diagnostic Trouble Code (DTC). The PCM
will store a DTC in electronic memory for any failureit detects. See Using On-Board Diagnostic System in
this group for more information.
DIAGNOSIS
When operating normally, the indicator lamp on
models with the base instrument cluster will light
when the ignition switch is turned to the ON or
START position. After the engine starts, the indicator
lamp goes off. With the engine running, the charge
indicator lamp should light only when there is a
problem in the charging system (base cluster only).
On models with a voltmeter, when the ignition
switch is turned to the ON position, battery potential
will register on the meter. During engine cranking a
lower voltage will appear on the meter. With the en-
gine running, a voltage reading higher than the first
reading (ignition in ON) should register.
The following procedures may be used to diagnose
the charging system if:
²the indicator or voltmeter do not operate properly
²an undercharged or overcharged battery condition
occurs.
Remember that an undercharged battery is often
caused by:
Fig. 1 Charging System Components (Typical)
JBATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS 8A - 17

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JEEP YJ 1995 Service And Repair Manual ²accessories being left on with the engine not run-
ning
²a faulty or improperly adjusted switch that allows
a lamp to stay on (see Ignition-Off Draw, in this
group).
INSPECTION
(1) Inspect conditio

²accessories being left on with the engine not run-
ning
²a faulty or improperly adjusted switch that allows
a lamp to stay on (see Ignition-Off Draw, in this
group).
INSPECTION
(1) Inspect condition of battery cable terminals,
battery posts, connections at engine block, starter so-
lenoid and relay. They should be clean and tight. Re-
pair as required.
(2) Inspect all fuses in the fuseblock module and
Power Distribution Center (PDC) for tightness in re-
ceptacles. They should be properly installed and
tight. Repair or replace as required.
(3) Inspect the electrolyte level in the battery. If
cell caps are removable, add water if required. If cell
caps are not removable, replace battery if electrolyte
level is low.
(4) Inspect generator mounting bolts for tightness.
Replace or tighten bolts, if required. Refer to Group
8B - Battery/Starter/Generator Service for torque
specifications.
(5) Inspect generator drive belt condition and ten-
sion. Tighten or replace belt as required. Refer to
Belt Tension Specifications in Group 7 - Cooling Sys-
tem.
(6) Inspect connections at generator field, battery
output, and ground terminals. Also check ground con-
nection at engine. They should all be clean and tight.
Repair as required.
OUTPUT WIRE RESISTANCE TEST
This test will show the amount of voltage drop
across the generator output wire, from the generator
battery terminal to the battery positive post.
PREPARATION
(1) Before starting test make sure vehicle has a
fully-charged battery. See Battery in this group for
more information.
(2) Turn ignition switch to OFF.
(3) Disconnect negative cable from battery.
(4) Disconnect generator output wire from genera-
tor battery output terminal.
(5) Connect a 0-150 ampere scale DC ammeter
(Fig. 2). Install in series between generator battery
output terminal and disconnected generator output
wire. Connect positive lead to generator battery out-
put terminal and negative lead to disconnected gen-
erator output wire.
(6) Connect positive lead of a test voltmeter (range
0-18 volts minimum) to disconnected generator out-
put wire. Connect negative lead of test voltmeter to
battery positive cable at positive post.
(7) Connect one end of a jumper wire to ground
and with other end probe green K20 field wire at
back of generator (Fig. 2). This will generate a DTC.CAUTION: Do not connect green/orange A142 field
wire to ground. Refer to Group 8W - Wiring Dia-
grams for more information.
(8) Connect an engine tachometer, then connect
battery negative cable to battery.
(9) Connect a variable carbon pile rheostat be-
tween battery terminals. Be sure carbon pile is in
OPEN or OFF position before connecting leads. See
Load Test in this group for instructions.
TEST
(1) Start engine. Immediately after starting, re-
duce engine speed to idle.
(2) Adjust engine speed and carbon pile to main-
tain 20 amperes flowing in circuit. Observe voltmeter
reading. Voltmeter reading should not exceed 0.5
volts.
RESULTS
If a higher voltage drop is indicated, inspect, clean
and tighten all connections. This includes any con-
nection between generator battery output terminal
and battery positive post. A voltage drop test may be
performed at each connection to locate the connection
with excessive resistance. If resistance tests satisfac-
torily, reduce engine speed, turn OFF carbon pile and
turn OFF ignition switch.
(1) Disconnect negative cable from battery.
(2) Remove test ammeter, voltmeter, carbon pile,
and tachometer.
(3) Remove jumper wire.
(4) Connect generator output wire to generator
battery output terminal. Tighten nut to 8.561.5 Nzm
(75615 in. lbs.).
(5) Connect negative cable to battery.
(6) Use DRB scan tool to erase DTC.
CURRENT OUTPUT TEST
The generator current output test determines
whether generator can deliver its rated current out-
put.
PREPARATION
(1) Before starting test make sure vehicle has a
fully-charged battery. See Battery in this group for
more information.
(2) Disconnect negative cable from battery.
(3) Disconnect generator output wire at the gener-
ator battery output terminal.
(4) Connect a 0-150 ampere scale DC ammeter
(Fig. 3). Install in series between generator battery
output terminal and disconnected generator output
wire. Connect positive lead to generator battery out-
put terminal and negative lead to disconnected gen-
erator output wire.
8A - 18 BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICSJ

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JEEP YJ 1995 Service And Repair Manual (5) Connect positive lead of a test voltmeter (range
0-18 volts minimum) to generator battery output ter-
minal.
(6) Connect negative lead of test voltmeter to a
good ground.
(7) Connect an engine tac

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