battery location DODGE RAM 1500 1998 2.G User Guide

Large eyelet type terminals are crimped onto the
opposite end of the battery cable wire and then sol-
der-dipped. The battery positive cable wires have a
red insulating jacket to provide visual identification
and feature a larger female battery terminal clamp
to allow connection to the larger battery positive ter-
minal post. The battery negative cable wires have a
black insulating jacket and a smaller female battery
terminal clamp.
OPERATION
The battery cables connect the battery terminal
posts to the vehicle electrical system. These cables
also provide a return path for electrical current gen-
erated by the charging system for restoring the volt-
age potential of the battery. The female battery
terminal clamps on the ends of the battery cable
wires provide a strong and reliable connection of the
battery cable to the battery terminal posts. The ter-
minal pinch bolts allow the female terminal clamps
to be tightened around the male terminal posts on
the top of the battery. The eyelet terminals secured
to the ends of the battery cable wires opposite the
female battery terminal clamps provide secure and
reliable connection of the battery to the vehicle elec-
trical system.
DIAGNOSIS AND TESTING - BATTERY CABLES
A voltage drop test will determine if there is exces-
sive resistance in the battery cable terminal connec-
tions or the battery cables. If excessive resistance is
found in the battery cable connections, the connec-
tion point should be disassembled, cleaned of all cor-
rosion or foreign material, then reassembled.
Following reassembly, check the voltage drop for the
battery cable connection and the battery cable again
to confirm repair.
When performing the voltage drop test, it is impor-
tant to remember that the voltage drop is giving an
indication of the resistance between the two points at
which the voltmeter probes are attached.EXAM-
PLE:When testing the resistance of the battery pos-
itive cable, touch the voltmeter leads to the battery
positive cable terminal clamp and to the battery pos-
itive cable eyelet terminal at the starter solenoid
B(+) terminal stud. If you probe the battery positive
terminal post and the battery positive cable eyelet
terminal at the starter solenoid B(+) terminal stud,
you are reading the combined voltage drop in the
battery positive cable terminal clamp-to-terminal
post connection and the battery positive cable.
VOLTAGE DROP TEST
WARNING: MODELS EQUIPPED WITH A DIESEL
ENGINE HAVE AN AUTOMATIC SHUTDOWN (ASD)RELAY LOCATED IN THE POWER DISTRIBUTION
CENTER (PDC). REMOVAL OF THE ASD RELAY
MAY NOT PREVENT THE DIESEL ENGINE FROM
STARTING. BE CERTAIN TO DISCONNECT THE
FUEL SHUTDOWN SOLENOID WIRE HARNESS
CONNECTOR TO PREVENT THE ENGINE FROM
STARTING. FAILURE TO DO SO MAY RESULT IN
PERSONAL INJURY.
The following operation will require a voltmeter
accurate to 1/10 (0.10) volt. Before performing this
test, be certain that the following procedures are
accomplished:
²The battery is fully-charged and tested (Refer to
8 - ELECTRICAL/BATTERY SYSTEM/BATTERY -
STANDARD PROCEDURE).
²Fully engage the parking brake.
²If the vehicle is equipped with an automatic
transmission, place the gearshift selector lever in the
Park position. If the vehicle is equipped with a man-
ual transmission, place the gearshift selector lever in
the Neutral position and block the clutch pedal in the
fully depressed position.
²Verify that all lamps and accessories are turned
off.
²To prevent a gasoline engine from starting,
remove the Automatic ShutDown (ASD) relay. The
ASD relay is located in the Integrated Power Module
(IPM), in the engine compartment. See the fuse and
relay layout label on the underside of the IPM cover
for ASD relay identification and location.
(1) Connect the positive lead of the voltmeter to
the battery negative terminal post. Connect the neg-
ative lead of the voltmeter to the battery negative
cable terminal clamp (Fig. 11). Rotate and hold the
ignition switch in the Start position. Observe the
voltmeter. If voltage is detected, correct the poor con-
nection between the battery negative cable terminal
clamp and the battery negative terminal post.
NOTE: If the vehicle is equipped with two 12v bat-
teries, step #1 must be performed twice, once for
each battery.
(2) Connect the positive lead of the voltmeter to
the battery positive terminal post. Connect the nega-
tive lead of the voltmeter to the battery positive cable
terminal clamp (Fig. 12). Rotate and hold the ignition
switch in the Start position. Observe the voltmeter. If
voltage is detected, correct the poor connection
between the battery positive cable terminal clamp
and the battery positive terminal post.
NOTE: If the vehicle is equipped with two 12v bat-
teries, step #2 must be performed twice, once for
each battery.
DRBATTERY SYSTEM 8F - 15
BATTERY CABLES (Continued)

(2) Disconnect and isolate the remote battery neg-
ative cable terminal.
(3) Remove the battery from the vehicle. Refer to
the procedure in this group.
(4) One at a time, trace the battery cable retaining
pushpins, fasteners and routing clips until the cable
is free from the vehicle.
(5) Remove the battery cable from the engine com-
partment.
INSTALLATION
(1) Position the battery cable in the engine com-
partment.
(2) One at a time, install the battery cable retain-
ing pushpins, fasteners and routing clips until the
cable is installed exactly where it was in the vehicle.
Refer to Wiring for illustrations.
(3) Install the battery in the vehicle. Refer to the
procedure in this group.
(4) Connect the battery negative cable terminal.
BATTERY TRAY
DESCRIPTION
The molded plastic tray battery tray is located in
the left front corner of the engine compartment. On
this model, the battery tray also provides an anchor
point for the anti-lock brake controller, cruise control
servo (if equipped) and the integrated power module
(Fig. 15). The battery hold down hardware is con-
tained within the battery tray. A hole in the bottom
of the battery tray is fitted with a battery tempera-
ture sensor. Refer to Charging System for more infor-
mation on the battery temperature sensor.
OPERATION
The battery tray and the battery hold down hard-
ware combine to secure and stabilize the battery in
the engine compartment, which prevents battery
movement during even the most extreme vehicle
operation. Unrestrained battery movement during
vehicle operation could result in damage to the vehi-
cle, the battery, or both.
REMOVAL
LEFT SIDE
(1) Remove the battery from the battery tray
(Refer to 8 - ELECTRICAL/BATTERY SYSTEM/BAT-
TERY - REMOVAL).
(2) Remove the integrated power module (Refer to
8 - ELECTRICAL/POWER DISTRIBUTION/INTEL-
LIGENT POWER MODULE - REMOVAL).
(3) Disconnect the wire harness retainers from the
battery tray assembly.
(4) Remove the anti-lock brake controller (if
equipped) retaining bolts and support the brake con-
troller with mechanics wire. It is not necessary to
completely remove the anti-lock brake control unit.
(5) Remove the left front wheelhouse splash shiel-
d(Refer to 23 - BODY/EXTERIOR/LF WHEEL-
HOUSE SPLASH SHIELD - REMOVAL).
(6) Mark the location of the cruise servo (if
equipped) and remove the retaining screws. Position
the servo out of the way.
(7) Remove the battery temperature sensor from
the battery tray (Refer to 8 - ELECTRICAL/CHARG-
ING/BATTERY TEMPERATURE SENSOR -
REMOVAL).
(8) Disconnect the purge solenoid from its mount-
ing bracket.
(9) Disconnect the left front fender ground wire.
(10) Remove the remaining battery tray retaining
bolts (Fig. 16).
(11) Remove the battery tray from the vehicle.
RIGHT SIDE
(1) Remove the battery from the battery tray
(Refer to 8 - ELECTRICAL/BATTERY SYSTEM/BAT-
TERY - REMOVAL).
Fig. 15 DR Battery Tray
1 - BATTERY TRAY ASSEMBLY
2 - BATTERY TEMPERATURE SENSOR
3 - ANTI-LOCK BRAKE CONTROLLER MOUNTING LOCATION
4 - INTEGRATED POWER MODULE MOUNTING SANCTION
DRBATTERY SYSTEM 8F - 17
BATTERY CABLES (Continued)

DESCRIPTION N´m Ft. Lbs. In. Lbs.
Generator (short)
Horizontal Mounting Bolt -
3.7L / 4.7L Engines74 55 -
Generator B+ Output
Cable Terminal Nut12 - 108
BATTERY TEMPERATURE
SENSOR
DESCRIPTION
The Battery Temperature Sensor (BTS) is attached
to the battery tray located under the battery.
OPERATION
The BTS is used to determine the battery temper-
ature and control battery charging rate. This temper-
ature data, along with data from monitored line
voltage, is used by the PCM (ECM Diesel) to vary the
battery charging rate. System voltage will be higher
at colder temperatures and is gradually reduced at
warmer temperatures.
The PCM sends 5 volts to the sensor and is
grounded through the sensor return line. As temper-
ature increases, resistance in the sensor decreases
and the detection voltage at the PCM increases.
The BTS is also used for OBD II diagnostics. Cer-
tain faults and OBD II monitors are either enabled
or disabled, depending upon BTS input (for example,
disable purge and enable Leak Detection Pump
(LDP) and O2 sensor heater tests). Most OBD II
monitors are disabled below 20ÉF.
REMOVAL
The battery temperature sensor is located under
the vehicle battery and is attached (snapped into) a
mounting hole on battery tray (Fig. 1).
(1) Remove battery. Refer to 8, Battery for proce-
dures.
(2) Pry sensor straight up from battery tray
mounting hole to gain access to electrical connector
(Fig. 1).
(3) Disconnect sensor from engine wire harness
electrical connector.
INSTALLATION
The battery temperature sensor is located under
the vehicle battery and is attached (snapped into) a
mounting hole on battery tray.
(1) Pull electrical connector up through mounting
hole in top of battery tray.
(2) Connect sensor.
(3) Snap sensor into battery tray.(4) Install battery. Refer to 8, Battery for proce-
dures.
GENERATOR
DESCRIPTION
The generator is belt-driven by the engine using a
serpentine type drive belt. It is serviced only as a
complete assembly. If the generator fails for any rea-
son, the entire assembly must be replaced.
OPERATION
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.
Fig. 1 BATTERY TEMPERATURE SENSOR
LOCATION
1 - BATTERY TEMP. SENSOR
2 - BATTERY
3 - SENSOR ELEC. CONNECT.
4 - BATTERY TRAY
DRCHARGING 8F - 21
CHARGING (Continued)

TESTING
COLD CRANKING TEST
For complete starter wiring circuit diagrams, refer
to 8, Wiring Diagrams. The battery must be fully-
charged and load-tested before proceeding. Refer to
Batteryin 8, Battery.
(1) Connect volt-ampere tester to battery terminals
(Fig. 1). See instructions provided by manufacturer of
volt-ampere tester being used.Note: Certain diesel
equipped models use dual batteries. If equipped
with dual battery system, tester should be con-
nected to battery on left side of vehicle only.
Also, tester current reading must be taken from
positive battery cable lead that connects to
starter motor.
(2) Fully engage parking brake.
(3) If equipped with manual transmission, place
gearshift selector lever in Neutral position and block
clutch pedal in fully depressed position. If equipped
with automatic transmission, place gearshift selector
lever in Park position.
(4) Verify that all lamps and accessories are
turned off.
(5) To prevent a gasoline engine from starting,
remove Automatic ShutDown (ASD) relay. To prevent
a diesel engine from starting, remove Fuel Pump
Relay. These relays are located in Power Distribution
Center (PDC). Refer to label on PDC cover for relay
location.
WARNING: IF EQUIPPED WITH DIESEL ENGINE,
ATTEMPT TO START ENGINE A FEW TIMES
BEFORE PROCEEDING WITH FOLLOWING STEP.(6) Rotate and hold ignition switch in Start posi-
tion. Note cranking voltage and current (amperage)
draw readings shown on volt-ampere tester.
(a) If voltage reads below 9.6 volts, refer to
Starter Motorin Diagnosis and Testing. If starter
motor is OK, refer toEngine Diagnosisin 9,
Engine for further testing of engine. If starter
motor is not OK, replace faulty starter motor.
(b) If voltage reads above 9.6 volts and current
(amperage) draw reads below specifications, refer
toFeed Circuit Testin this section.
(c) If voltage reads 12.5 volts or greater and
starter motor does not turn, refer toControl Cir-
cuit Testingin this section.
(d) If voltage reads 12.5 volts or greater and
starter motor turns very slowly, refer toFeed Cir-
cuit Testin this section.
NOTE: A cold engine will increase starter current
(amperage) draw reading, and reduce battery volt-
age reading.
FEED CIRCUIT TEST
The starter feed circuit test (voltage drop method)
will determine if there is excessive resistance in
high-amperage feed circuit. For complete starter wir-
ing circuit diagrams, refer 8, Wiring Diagrams.
When performing these tests, it is important to
remember that voltage drop is giving an indication of
resistance between two points at which voltmeter
probes are attached.
Example:When testing resistance of positive bat-
tery cable, touch voltmeter leads to positive battery
cable clamp and cable connector at starter solenoid.
If you probe positive battery terminal post and cable
connector at starter solenoid, you are reading com-
bined voltage drop in positive battery cable clamp-to-
terminal post connection and positive battery cable.
The following operation will require a voltmeter
accurate to 1/10 (0.10) volt. Before performing tests,
be certain that following procedures are accom-
plished:
²Battery is fully-charged and load-tested. Refer to
Batteryin 8, Battery.
²Fully engage parking brake.
²If equipped with manual transmission, place
gearshift selector lever in Neutral position and block
clutch pedal in fully depressed position. If equipped
with automatic transmission, place gearshift selector
lever in Park position.
²Verify that all lamps and accessories are turned
off.
Fig. 1 VOLTS-AMPS TESTER CONNECTIONS -
TYPICAL
1 - POSITIVE CLAMP
2 - NEGATIVE CLAMP
3 - INDUCTION AMMETER CLAMP
DRSTARTING 8F - 29
STARTING (Continued)

²To prevent a gasoline engine from starting,
remove Automatic ShutDown (ASD) relay. To prevent
a diesel engine from starting, remove Fuel Pump
Relay. These relays are located in Power Distribution
Center (PDC). Refer to label on PDC cover for relay
location.
(1) Connect positive lead of voltmeter to negative
battery cable terminal post. Connect negative lead of
voltmeter to negative battery cable clamp (Fig. 2).
Rotate and hold ignition switch in Start position.
Observe voltmeter. If voltage is detected, correct poor
contact between cable clamp and terminal post.
Note: Certain diesel equipped models use dual
batteries. If equipped with dual battery system,
procedure must be performed twice, once for
each battery.
(2) Connect positive lead of voltmeter to positive
battery terminal post. Connect negative lead of volt-
meter to battery positive cable clamp (Fig. 3). Rotate
and hold ignition switch in Start position. Observe
voltmeter. If voltage is detected, correct poor contact
between cable clamp and terminal post.Note: Cer-
tain diesel equipped models use dual batteries.
If equipped with dual battery system, this pro-
cedure must be performed twice, once for each
battery.
(3) Connect voltmeter to measure between battery
positive terminal post and starter solenoid battery
terminal stud (Fig. 4). Rotate and hold ignition
switch in Start position. Observe voltmeter. If read-
ing is above 0.2 volt, clean and tighten battery cable
connection at solenoid. Repeat test. If reading is still
above 0.2 volt, replace faulty positive battery cable.
Note: Certain diesel equipped models use dual
batteries. If equipped with dual battery system,
this procedure must be performed on driver
side battery only.(4) Connect voltmeter to measure between nega-
tive battery terminal post and a good clean ground
on engine block (Fig. 5). Rotate and hold ignition
switch in Start position. Observe voltmeter. If read-
ing is above 0.2 volt, clean and tighten negative bat-
tery cable attachment on engine block. Repeat test. If
reading is still above 0.2 volt, replace faulty negative
battery cable.Note: Certain diesel equipped mod-
els use dual batteries. If equipped with dual
battery system, this procedure must be per-
formed twice, once for each battery.
Fig. 2 TEST BATTERY NEGATIVE CONNECTION
RESISTANCE - TYPICAL
1 - VOLTMETER
2 - BATTERY
Fig. 3 TEST BATTERY POSITIVE CONNECTION
RESISTANCE - TYPICAL
1 - VOLTMETER
2 - BATTERY
Fig. 4 TEST BATTERY POSITIVE CABLE
RESISTANCE - TYPICAL
1 - BATTERY
2 - VOLTMETER
3 - STARTER MOTOR
8F - 30 STARTINGDR
STARTING (Continued)

5.7L
(1) Connect solenoid wire to starter motor (snaps
on).
(2) Position battery cable to solenoid stud. Install
and tighten battery cable eyelet nut. Refer to Torque
Specifications. Do not allow starter motor to hang
from wire harness.
(3) Position starter motor to engine.
(4) If equipped with automatic transmission, slide
cooler tube bracket into position.
(5) Install and tighten both mounting bolts. Refer
to Torque Specifications.
(6) Lower vehicle.
(7) Connect negative battery cable.
5.9L Diesel
(1)If Equipped:Position and hold aluminum
spacer to rear of starter while positioning starter to
engine.
(2) Connect solenoid wire to starter motor. Tighten
nut.
(3) Position battery cable to starter stud. Install
and tighten battery cable nut. Refer to Torque Spec-
ifications. Do not allow starter motor to hang from
wire harness.
(4) Position starter motor to transmission.
(5) If equipped with automatic transmission, slide
cooler tube bracket into position.
(6) Install and tighten 3 starter mounting bolts.
Refer to Torque Specifications.
(7) Lower vehicle.
(8) Connect both negative battery cables to both
batteries.
STARTER MOTOR RELAY
DESCRIPTION
The starter relay is an electromechanical device
that switches battery current to the pull-in coil of the
starter solenoid when ignition switch is turned to
Start position. The starter relay is located in the
Power Distribution Center (PDC) in the engine com-
partment. See PDC cover for relay identification and
location.
The starter relay is a International Standards
Organization (ISO) relay. Relays conforming to ISO
specifications have common physical dimensions, cur-
rent capacities, terminal patterns, and terminal func-
tions.
The starter relay cannot be repaired or adjusted. If
faulty or damaged, it must be replaced.
Fig. 12 STARTER R/I - 5.9L DIESEL
1 - MOUNTING BOLTS (3)
2 - STARTER MOTOR
3 - SPACER (CERTAIN TRANSMISSIONS)
Fig. 13 STARTER ELECTRICAL CONNECTORS -
5.9L DIESEL
1 - STARTER MOTOR
2 - BATTERY CABLE NUT
3 - SOLENOID NUT
4 - HARNESS ASSEMBLY
DRSTARTING 8F - 35
STARTER MOTOR (Continued)

OPERATION
The ISO relay consists of an electromagnetic coil, a
resistor or diode, and three (two fixed and one mov-
able) electrical contacts. The movable (common feed)
relay contact is held against one of the fixed contacts
(normally closed) by spring pressure. When electro-
magnetic coil is energized, it draws the movable con-
tact away from normally closed fixed contact, and
holds it against the other (normally open) fixed con-
tact.
When electromagnetic coil is de-energized, spring
pressure returns movable contact to normally closed
position. The resistor or diode is connected in parallel
with electromagnetic coil within relay, and helps to
dissipate voltage spikes produced when coil is de-en-
ergized.
DIAGNOSIS AND TESTING - STARTER RELAY
The starter relay (Fig. 14) is located in Power Dis-
tribution Center (PDC). Refer to PDC cover for relay
identification and location. For complete starter relay
wiring circuit diagrams, refer to 8, Wiring Diagrams.
(1) Remove starter relay from PDC.
(2) A relay in de-energized position should have
continuity between terminals 87A and 30, and no
continuity between terminals 87 and 30. If OK, go to
Step 3. If not OK, replace faulty relay.
(3) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 75   5 ohms. If OK, go to Step
4. If not OK, replace faulty relay.
(4) Connect 12V 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, perform Relay Circuit Test that fol-
lows. If not OK, replace faulty relay.
RELAY CIRCUIT TEST
(1) The relay common feed terminal cavity (30) is
connected to battery voltage and should be hot at all
times. If OK, go to Step 2. If not OK, repair open cir-
cuit to fuse in PDC as required.
(2) The relay normally closed terminal (87A) is
connected to terminal 30 in the de-energized position,
but is not used for this application. Go to Step 3.
(3) The relay normally open terminal (87) is con-
nected to common feed terminal (30) in the energized
position. This terminal supplies battery voltage to
starter solenoid field coils. There should be continu-
ity between cavity for relay terminal 87 and starter
solenoid terminal at all times. If OK, go to Step 4. If
not OK, repair open circuit to starter solenoid as
required.(4) The coil battery terminal (86) is connected to
electromagnet in relay. It is energized when ignition
switch is held in Start position. On vehicles with
manual transmission, clutch pedal must be fully
depressed for this test. Check for battery voltage at
cavity for relay terminal 86 with ignition switch in
Start position, and no voltage when ignition switch is
released to On position. If OK, go to Step 5. If not
OK with automatic transmission, check for open or
short circuit to ignition switch and repair, if required.
If circuit to ignition switch is OK, refer toIgnition
Switch and Key Lock Cylinder. If not OK with a
manual transmission, check circuit between relay
and clutch pedal position switch for open or a short.
If circuit is OK, refer toClutch Pedal Position
Switchin 6 , Clutch.
(5) The coil ground terminal (85) is connected to
the electromagnet in the relay. On vehicles with
manual transmission, it is grounded at all times. On
vehicles with automatic transmission, it is grounded
through park/neutral position switch only when gear-
shift selector lever is in Park or Neutral positions.
Check for continuity to ground at cavity for relay ter-
minal 85. If not OK with manual transmission,
repair circuit to ground as required. If not OK with
automatic transmission, check for pen or short circuit
to park/neutral position switch and repair, if
required. If circuit to park/neutral position switch is
OK, refer toPark/Neutral Position Switchin 21,
Transmission.
Fig. 14 TYPE 1 RELAY
TERMINAL LEGEND
NUMBER IDENTIFICATION
30 COMMON FEED
85 COIL GROUND
86 COIL BATTERY
87 NORMALLY OPEN
87A NORMALLY CLOSED
8F - 36 STARTINGDR
STARTER MOTOR RELAY (Continued)

REMOVAL
The starter relay is located in the Power Distribu-
tion Center (PDC) (Fig. 15). Refer to label on PDC
cover for relay location.
(1) Disconnect and isolate negative battery cable.
(2) Remove cover from Power Distribution Center
(PDC) for relay identification and location.
(3) Remove starter relay from PDC.
(4) Check condition of relay terminals and PDC
connector terminals for damage or corrosion. Repair
if necessary before installing relay.
(5) Check for pin height (pin height should be the
same for all terminals within the PDC connector).
Repair if necessary before installing relay.
INSTALLATION
(1) Push down firmly on starter relay until termi-
nals are fully seated into PDC receptacle.
(2) Install PDC cover.
(3) Connect battery cable.
Fig. 15 PDC LOCATION
1 - BATTERY
2 - INTEGRATED POWER MODULE (IPM)
DRSTARTING 8F - 37
STARTER MOTOR RELAY (Continued)

DIAGNOSIS AND TESTING - REAR WINDOW
DEFOGGER SYSTEM
For circuit descriptions and diagrams, refer to Rear
Window Defogger in Wiring Diagrams. The operation
of the electrically heated rear window defogger sys-
tem can be confirmed in one of the following man-
ners:
1. Turn the ignition switch to the On position.
While monitoring the instrument panel voltmeter, set
the defogger switch in the On position. When the
defogger switch is turned On, a distinct voltmeter
needle deflection should be noted.
2. Turn the ignition switch to the On position. Set
the defogger switch in the On position. The rear win-
dow defogger operation can be checked by feeling the
rear window or outside rear view mirror glass. A dis-
tinct difference in temperature between the grid lines
and the adjacent clear glass or the mirror glass can
be detected within three to four minutes of operation.
3. Using a 12-volt DC voltmeter, contact the rear
glass heating grid terminal A (right side) with the
negative lead, and terminal B (left side) with the pos-
itive lead (Fig. 1). The voltmeter should read battery
voltage.
The above checks will confirm system operation.
Illumination of the defogger switch indicator lamp
means that there is electrical current available at the
output of the rear window defogger logic and timer
circuitry, but does not confirm that the electrical cur-
rent is reaching the rear glass heating grid lines.
If the defogger system does not operate, the prob-
lem should be isolated in the following manner:(1) Confirm that the ignition switch is in the On
position.
(2) Make sure that the rear glass heating grid feed
and ground wires are connected to the glass. Confirm
that the ground wire has continuity to ground.
(3) Check the fuses in the power distribution cen-
ter (PDC) and in the junction block. The fuses must
be tight in their receptacles and all electrical connec-
tions must be secure.
When the above steps have been completed and the
rear glass heating grid is still inoperative, one or
more of the following could be faulty:
²Rear window switch in the A/C-heater control..
²Rear window grid lines (all grid lines would
have to be broken or one of the feed wires discon-
nected for the entire system to be inoperative).
If setting the defogger switch to the On position
produces a severe voltmeter deflection, check for a
short circuit between the rear window switch defog-
ger relay output and the rear glass heating grid.
REAR WINDOW DEFOGGER
RELAY
DESCRIPTION
The rear window defogger relay (Fig. 2) is a Inter-
national Standards Organization (ISO) micro-relay.
Relays conforming to the ISO specifications have
common physical dimensions, current capacities, ter-
minal patterns, and terminal functions. The ISO
micro-relay terminal functions are the same as a con-
ventional ISO relay. However, the ISO micro-relay
terminal pattern (or footprint) is different, the cur-
rent capacity is lower, and the physical dimensions
are smaller than those of the conventional ISO relay.
The rear window defogger relay is located in the
power distribution center (PDC) in the engine com-
partment. Refer to the PDC label for rear window
defogger relay identification and location.
The black, molded plastic case is the most visible
component of the rear window defogger relay. Five
male spade-type terminals extend from the bottom of
the base to connect the relay to the vehicle electrical
system, and the ISO designation for each terminal is
molded into the base adjacent to each terminal. The
ISO terminal designations are as follows:
²30 (Common Feed)- This terminal is con-
nected to the movable contact point of the relay.
²85 (Coil Ground)- This terminal is connected
to the ground feed side of the relay control coil.
²86 (Coil Battery)- This terminal is connected
to the battery feed side of the relay control coil.
²87 (Normally Open)- This terminal is con-
nected to the normally open fixed contact point of the
relay.
Fig. 1 Grid Line Test - Typical
1 - VIEW FROM INSIDE VEHICLE
2 - REAR WINDOW DEFOGGER
3 - BUS BARS
4 - VOLTAGE FEED (A)
5 - VOLTMETER
6 - MID-POINT (C)
7 - PICK-UP LEADS
8 - GROUND (B)
8G - 2 HEATED GLASSDR
HEATED GLASS (Continued)

²87A (Normally Closed)- This terminal is con-
nected to the normally closed fixed contact point of
the relay.
The rear window defogger relay cannot be adjusted
or repaired. If the relay is damaged or faulty, it must
be replaced.
OPERATION
The rear window defogger relay is an electrome-
chanical switch that uses a low current input from
the integrated power module (IPM) to control the
high current output to the rear window defogger
grid. The movable common feed contact point is held
against the fixed normally closed contact point by
spring pressure. When the relay coil is energized, an
electromagnetic field is produced by the coil wind-
ings. This electromagnetic field draws the movable
relay contact point away from the fixed normally
closed contact point, and holds it against the fixed
normally open contact point. When the relay coil is
de-energized, spring pressure returns the movable
contact point back against the fixed normally closed
contact point. The resistor or diode is connected in
parallel with the relay coil in the relay, and helps to
dissipate voltage spikes and electromagnetic interfer-
ence that can be generated as the electromagnetic
field of the relay coil collapses.
The rear window defogger relay terminals are con-
nected to the vehicle electrical system through a
receptacle in the IPM. The inputs and outputs of the
rear window defogger relay include:
²The common feed terminal (30) receives a bat-
tery current input from fuse 27 (15 amp) in the IPM
through a fused B(+) circuit at all times.²The coil ground terminal (87) receives a ground
input from the A/C-heater control when the A/C-
heater control electronically pulls the control circuit
to ground.
²The coil battery terminal (85) receives a battery
current input from fuse 36 (10 amp) in the IPM
through a fused B(+) circuit only when the ignition
switch is in the Run position.
²The normally open terminal (86) provides a bat-
tery current output to the rear window defogger and
heated power mirrors (when equipped) through the
relay output circuit only when the rear window
defogger relay coil is energized.
²The normally closed terminal (87A) is not con-
nected to any circuit in this application, but provides
a battery current output only when the rear window
defogger relay coil is de-energized.
The rear window defogger relay cannot be repaired
and, if faulty or damaged, it must be replaced. Refer
to the appropriate wiring information for diagnosis
and testing of the micro-relay and for complete rear
window defogger system wiring diagrams.
REMOVAL
(1)Disconnect and isolate the negative battery cable.
(2) Remove the cover from the integrated power
module (IPM) (Fig. 3).
(3) Refer to the fuse and relay layout map on the
inner surface of the IPM cover for rear window defog-
ger relay identification and location.
(4) Remove the rear window defogger relay from
the IPM.
Fig. 2 Rear Window Defogger Relay
1 - RELAY TERMINALS
2 - RELAY CAVITIES
Fig. 3 Integrated Power Module (IPM)
1 - BATTERY
2 - INTEGRATED POWER MODULE (IPM)
DRHEATED GLASS 8G - 3
REAR WINDOW DEFOGGER RELAY (Continued)