Spark

Rear Window Defogger Description and Operation

The rear window demister is controlled by the rear demister relay through a high side drive control circuit. Battery voltage is supplied to the switch side of the relay at all times and when the relay is energised battery voltage is supplied to the rear window demister control circuit The rear demister relay is controlled by the rear window demister switch through a low side drive control circuit. Ignition voltage is supplied to the relay coil and when the rear demister switch is pressed the relay control circuit is grounded and the relay will be energised.