Description and operation

Rear glass heating grid

The heated rear window glass has two electrically conductive vertical bus bars and a series of horizontal grid lines made of a silver-ceramic material, which is baked on and bonded to the inside surface of the glass. The grid lines and bus bars comprise a parallel electrical circuit.

When the rear window defogger switch is placed in the On position, electrical current is directed to the rear window grid lines through the bus bars. The grid lines heat the rear window to clear the surface of fog or snow. Protection for the heating grid circuit is provided by a fuse in the Power Distribution Center (PDC).

The grid lines and bus bars are highly resistant to abrasion. However, it is possible for an open circuit to occur in an individual grid line, resulting in no current flow through the line.

The grid lines can be damaged or scraped off with sharp instruments. Care should be taken when cleaning the glass or removing foreign materials, decals, or stickers from the glass. Normal glass cleaning solvents or hot water used with rags or toweling is recommended.

A repair kit is available to repair the grid lines and bus bars, or to reinstall the heated glass terminals.

Outside mirror heating grid

Vehicles equipped with the optional heated mirror system have an electric heating grid located behind the mirror glass of each outside rear view mirror.

The heated mirrors are controlled by the rear window defogger switch. Electrical current is directed to the heating grid inside the mirror only when the rear window defogger switch is in the On position.

If the outside mirror heating grids are both inoperative, see Rear Window Defogger System in the Diagnosis and Testing section of this group. If only one of the outside mirror heating grids is inoperative, see Power Mirror System in the Diagnosis and Testing section of Group 8T - Power Mirror Systems for diagnosis of the outside mirror heating grid.

The heating grid behind each outside mirror glass cannot be repaired and, if faulty or damaged, the entire power mirror unit must be replaced. Refer to Power Mirror in the Removal and Installation section of Group 8T - Power Mirror Systems for the service procedures.

Defogger switch

The rear window defogger switch is integral to the rear window switch pod, which includes the rear wiper and washer switches. The rear window switch pod is installed in the instrument panel lower bezel, which is located near the center of the lower instrument panel, below the heater and air conditioner controls.

The rear window switch pod also contains the rear window defogger logic and timer circuitry, an amber defogger indicator lamp, the rear window defogger relay, and two switch illumination lamps. The indicator and illumination lamps in the switch pod use incandescent bulbs, which can be serviced.

The momentary-type rear window defogger switch provides a hard wired ground signal to the rear window defogger logic and timer circuitry, each time it is depressed. The rear window defogger timer and logic circuitry responds by energizing or de-energizing the rear window defogger relay and the amber defogger indicator lamp, which lights to indicate when the defogger system is turned On. Energizing the rear window defogger relay provides electrical current to the rear window defogger grid.

The rear window switch pod cannot be repaired. If any function of the switch pod except lighting is faulty or damaged, the entire switch pod must be replaced.