When the ignition switch is on, voltage is supplied from the HVAC fuse to the rear window defogger relay and the heater-a/c control through circuit 41. The rear window defogger relay receives voltage from the REAR DEFOG circuit breaker through circuit 1040. When the rear defogger switch is pressed, voltage is momentarily applied to the solid state timer, sending a ground signal to the rear window defogger relay through circuit 193. This energizes the rear window defogger relay. When the rear window defogger relay is energized, voltage is sent from circuit 1040 to circuit 293. This sends voltage to the rear defogger grid which is also receiving ground from G401 through circuit 450, causing the rear defogger grid to heat up. The rear window defogger relay remains energized until the defog cycle is complete or the rear defogger switch is pressed a second time.

When the ignition switch is on and the rear defogger switch is pressed for the first time, the defog cycle lasts 10 minutes. However, further operation of the rear defogger will result in 5 minute defog cycles. The defog cycle is reset to 10 minutes when the ignition switch is turned off and back to on.

The defogger ON indicator is an LED that illuminates when the rear defogger is on.

In addition to turning on the rear defogger grid, circuit 293 also supplies voltage to the HEATED MIRROR fuse in the fuse block. From the HEATED MIRROR fuse, voltage is applied to the LH and RH outside rearview mirrors through circuit 267. The LH and RH outside rearview mirrors are connected to ground from G301 through circuit 750. This causes the defogger within the LH and RH outside rearview mirrors to defog the mirrors. The defog cycle is the same as described above concerning the rear defogger.