Heated Glass Element: Description and Operation

CIRCUIT OPERATION
Whenever the ignition switch is in the "ON" position, ignition voltage is applied through the GAUGE Fuse to the coil of the Defogger Relay and to the Rear Defogger Switch through the Audio Alarm Module and Junction Block 3. Battery voltage is applied to the switch portion of the Defogger Relay at all times through the Defogger Fusible Link.

Whenever the Rear Defogger Switch is pressed ON, the Defogger Relay coil is grounded through the Rear Defogger Switch, Junction Block 3, Audio Alarm Module, Junction Block 1 and Junction Connector I to G200. The Defogger Relay energizes, the contacts close and voltage is applied to the Rear Defogger. Since the Rear Defogger is a resistive element and is permanently grounded to G301, it begins to heat as soon as voltage is applied.

The energized Defogger Relay also provides voltage to the Rear Defogger Indicator through the DEF-I/UP Fuse. Since the Rear Defogger Indicator is permanently grounded through Junction Block 3, Junction Connector 3 and Junction Connector 1 to G200, the indicator lights as soon as voltage is applied.

The Rear Defogger Switch incorporates an integral timing circuit. When the Rear Defogger Switch is first pressed ON, the Rear Defogger will operate for 12-18 minutes and then shut off automatically. The Rear Defogger can be manually shut off if the Rear Defogger Switch is pressed again during the 12-18 minutes that the Rear Defogger is operating.

The Rear Defogger circuit also contains a noise filter to eliminate any interference when listening to tunes on the Radio when the Defogger is ON.