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

Whenever the Rear Defogger Switch is pressed ON, the Defogger Relay coil is grounded through the Defogger Switch, Junction Block 3, and the Splice Pack 256 to G 204. 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 G 301, it begins to heat as soon as the 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 the Splice Pack 256 to G 204 the indicator lights as soon as the 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 press again during the 12-18 minutes that the Rear Defogger is operating.