Voltage is applied at all times from the DEFOG/SEATS CKT BRKR 30A to the rear defogger timer/relay. When the ignition switch is turned to the RUN position, voltage is applied by the HVAC Fuse 6 to the rear defogger switch and the rear defogger timer/relay.

When the rear defogger switch is pressed, battery voltage, ignition voltage, and ground are momentarily applied to the solid state device within the rear defogger timer/relay. When all three of these inputs occur, the solid state device provides a ground to the solenoid within the rear defogger timer/relay. Voltage is supplied at all times to the solenoid through the DEFOG/SEATS CKT BRKR 30A. When the ground is applied to the solenoid, the switch contact within the rear defogger timer/relay closes providing voltage to the rear defogger grid. The rear defogger grid receives ground at all times. When the rear defogger grid receives voltage, the rear defogger operates.

The rear defogger timer/relay contains an internal timer in order to control the time the internal contacts are closed. The defog cycle lasts 10 minutes when the ignition switch is turned to the RUN position and the rear defogger switch is pressed for the first time.

When the rear defogger switch is pressed again after the 10 minute time out, the rear defogger will run in a 5 minute defog cycle. This rear defogger will run at 5 minute cycles each time the rear defogger switch is pressed until the ignition switch is turned to the OFF position and then back to the RUN position. The defog cycle will then reset to the original 10 minutes.

When the switch contact within the rear defogger timer/relay closes, voltage is not only provided to the rear defogger grid but also to the on indicator in the rear defogger switch. When this voltage is applied, the indicator turns on and stays on until the rear defogger is shut off or turns off after the 10 minute cycle. The indicator will turn on and remain on as long as the rear defogger is running. The on indicator turns off when the rear defogger turns off.