Jeep 1996 Grand Cherokee Service Manual - page 409
(2) Check for continuity between the ground cir-
cuit cavity of the switch pod 10-way wire harness
connector and a good ground. There should be conti-
nuity. If OK, go to Step 3. If not OK, repair the open
circuit as required.
(3) Using two jumper wires, connect the ground
circuit terminal in the 10-way connector receptacle
on the back of the switch pod housing to a good
ground, connect the fused rear window defogger relay
output circuit terminal of the 10-way connector
receptacle to a 12-volt battery feed. The defogger
switch LED should light. If OK, go to Step 4. If not
OK, replace the faulty switch pod.
(4) Check for continuity between the ground cir-
cuit and rear window defogger switch sense circuit
terminals of the 10-way connector receptacle on the
back of the switch pod housing. There should be con-
tinuity with the defogger switch button depressed,
and no continuity with the switch button released. If
OK, go to Step 5. If not OK, replace the faulty switch
pod.
(5) Unplug the white 24-way connector from the
body control module. Check for continuity between
the rear window defogger switch sense circuit cavity
of the switch pod 10-way wire harness connector and
a good ground. There should be no continuity. If OK,
go to Step 6. If not OK, repair the short circuit as
required.
(6) Check for continuity between the rear window
defogger switch sense circuit cavities of the switch
pod 10-way wire harness connector and the body con-
trol module white 24-way harness connector. There
should be continuity. If OK, see the Defogger Relay
diagnosis in this group. If not OK, repair the open
circuit as required.
DEFOGGER RELAY
RELAY TEST
The defogger relay is located in the junction block,
on the right cowl side panel below the instrument
panel in the passenger compartment. Remove the
defogger relay from the junction block as described in
this group to perform the following 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 Step 2. If not OK, replace the faulty relay.
(2) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 75
610 ohms. If OK, go to Step
3. If not OK, replace the 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, see the Relay Circuit Test in this
group. If not OK, replace the 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 the open
circuit to the PDC fuse 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 the common feed terminal (30) in the ener-
gized position. This terminal supplies battery voltage
to the fuse in the junction block that feeds the rear
glass heating grid and the defogger switch LED.
There should be continuity between the cavity for
relay terminal 87 and the rear glass heating grid/de-
fogger switch LED at all times. If OK, go to Step 4. If
not OK, check the fuse in the junction block and/or
repair the open circuit as required.
(4) The coil battery terminal (86) is connected to
the electromagnet in the relay. It is connected to bat-
tery voltage and should be hot at all times. Check for
battery voltage at the cavity for relay terminal 86. If
OK, go to Step 5. If not OK, repair the open circuit to
the PDC fuse as required.
(5) The coil ground terminal (85) is connected to
the electromagnet in the relay. This terminal is pro-
vided with ground by the Body Control Module
(BCM) to energize the rear glass heating grid and
defogger switch LED. There should be continuity to
the rear window defogger relay control circuit cavity
of the white 24-way BCM connector. If OK, use a
DRB scan tool and the proper Body Diagnostic Pro-
cedures Manual to diagnose the BCM. If not OK,
repair the open circuit as required.
Defogger Relay
8N - 4
ELECTRICALLY HEATED SYSTEMS
ZJ
DIAGNOSIS AND TESTING (Continued)