Heated Glass Element: Description and Operation

INTRODUCTION
For proper operation of the Rear Window Defogger system refer to the Owner's Manual.

Vehicles equipped with an electrically heated rear window defogger also have a 90 amp generator.

Rear Window Defogger Typical:

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 timer relay located in the A/C, heater or ATC control is used on all models.

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.

When the switch is turned to the ON position, current is directed to the rear defogger grid lines. The heated grid lines heat the rear glass to clear the surface of fog or frost.

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 recommended.

SYSTEM OPERATION

ATC Control Switch:

Heater Control Switch:

Heater-A/C ATC Control Switch
The control switch and timer relay are integrated into the Heater-A/C or ATC controls. Actuating the switch energizes the circuit allowing current to flow through the grid lines for ten minutes. Upon initial actuation, 5 minutes with each subsequent actuation or until either the switch or ignition is turned off. An indicating lamp illuminates a lens in laid in the control switch.

CIRCUIT OPERATION
Rear Window Defogger Antenna
The rear window defogger antenna is part of the rear window defogger grid.

Power for the antenna is supplied on circuit X60. This circuit is HOT when the radio is turned ON and is spliced in with the power amplifier.

Ground is supplied on circuit Z1.

Heated Rear Window
The heated rear window system uses a relay located internal to the A/C-Heater, or ATC, control. Circuity internal to the control provides the power and ground for the coil side of the relay. Power for the contact side of the relay is provided by circuit A4. This circuit originates at the battery positive terminal and is protected by a fusible link.

When the operator presses the switch in the control the contacts in the relay CLOSE connecting circuits A4 and C15. The C15 circuit connects from the control to the heated rear window grid. Circuit C15 also splices and provides power for the heated mirrors.

The heated rear window grid consists of two BUS bars and grid lines that form a parallel circuit. When current flows through the grid the grid lines heat up and transfer the heat to the window. Ground for the grid is provided on circuit Z1 and terminates at the right rear wheel well.