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Heated Glass Element: Description and Operation

HEATED GLASS
Rear Window Defogger
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. A control switch and a timing circuit are combined into the HVAC control assembly. A push button on the HVAC control assembly turns the defroster ON or OFF. Circuit protection is provided by a cartridge fuse located in the Power Distribution Center (PDC) for the heated grid circuit, and a fuse in the fuse block for the control circuit.

The defogger system is controlled by a momentary switch in the HVAC Control assembly. An amber indicator lamp in the HVAC Control assembly will light to indicate when the defogger system is turned on. The rear window switch also contains the defogger system control circuitry including the timer logic and the defogger relay

The defogger system will be automatically turned OFF after a programmed time interval of about ten minutes. After the initial time interval has expired, if the defogger switch is turned on again during the same ignition cycle, the defogger system will automatically turn OFF after about ten minutes.

The defogger system will automatically shut OFF if the ignition switch is turned to the OFF position, or it can be turned OFF manually by depressing the defogger switch a second time. Refer to the owner's manual in the vehicle glove box for more information on the features, use and operation of the defogger system.

REAR WINDOW DEFOGGER GRID
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. A control switch and a timing circuit are combined into the heating-A/C control assembly

A push-button on the heater-A/C control assembly turns the defroster ON and OFF

Circuit protection is provided by a cartridge fuse located in the Power Distribution Center (PDC) for the heated grid 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.

REAR WINDOW DEFOGGER SWITCH
The rear window defogger switch is integral to the heater-A/C control assembly

The rear window switch also contains the rear window defogger logic and timer circuitry, an LED defogger indicator lamp, the rear window defogger relay If faulty or damaged the entire controller assembly must be replaced.

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 cannot be repaired. If any function of the switch is faulty or damaged, the entire heater-A/C control assembly must be replaced.