ELECTRICALLY HEATED SYSTEMS
TABLE OF CONTENTS
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REAR WINDOW DEFOGGER..................1 HEATEDSEATS............................ 6
REAR WINDOW DEFOGGER
TABLE OF CONTENTS
page page
DESCRIPTION AND OPERATION
REAR WINDOW DEFOGGER SYSTEM .........1
DIAGNOSIS AND TESTING
SERVICE PROCEDURES....................2
A/C-HEATER AND ATC CONTROL HEAD........2
SYSTEM TEST............................2
GRID TEST ..............................2
FUSE AND ELECTRICAL SHORT TEST .........3
REAR WINDOW DEFOGGER RELAY...........3
SERVICE PROCEDURES
REPAIR GRID LINES, TERMINALS AND
PIGTAILS ..............................4
REMOVAL AND INSTALLATION
HEATER-A/C ATC CONTROL .................5
REAR WINDOW DEFOGGER RELAY...........5
DESCRIPTION AND OPERATION
REAR WINDOW DEFOGGER SYSTEM
DESCRIPTION
The Rear Window Defogger electrical system
involves the operation of the Heater-A/C or ATC Con-
trol Head, the Body Control Module (BCM), and the
rear Window Defogger Relay and wiring. The system
consists of a rear glass with two vertical bus bars
and a series of electrically connected grid lines fired
on the inside surface. The Body Control Module
(BCM) operates a relay located in the trunk area on
all models..
Vehicles with Rear Window Antenna refer to Group
8F, Audio Systems.
Vehicles equipped with an electrically heated rear
window defogger also have a 90 amp generator.
OPERATION
The passenger can push the Rear Widow Defogger
button on the Heater-A/C or ATC Control to defog the
rear glass. The system will only operate when the
ignition switch is in the run position. Once the Rear
Widow Defogger button is pushed. the button indica-
tor will light and the system will operate for a period
of time and then automatically turn off. Refer to the
owner’s manual for operation of the A/C-Heater or
ATC control.
When the rear window defogger relay is ON, cur-
rent is directed to the rear defogger grid lines. The
heated grid lines heat the rear glass to clear the sur-
face of fog or frost.
Circuit protection is provided by a fusible link,
located in the charging circuit, for the heated grid
circuit and by a fuse for the relay control circuit.
The A/C-Heater or the ATC control sends a signal
to the BCM, which indicates to the BCM that the
operator wants the rear window grid to heat. Refer to
the A/C-Heater or ATC Control section of the service
manual for details on how these modules interact. An
output wire from the BCM connects to the coil of the
rear window defogger relay. The other side of the coil
is connected to a fuse. The BCM turns on the relay
by connecting the output line of the BCM to vehicle
ground. The relay contacts will then close supplying
vehicle power to the rear window defogger grid.
CAUTION: Grid lines can be damaged or scraped
off with sharp instruments, care should be taken in
cleaning glass or removing foreign materials,
decals or stickers. Normal glass cleaning solvents
or hot water used with rags or toweling is recom-
mended.
LH ELECTRICALLY HEATED SYSTEMS 8N - 1
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