Captiva

Rear Window Defogger Description and Operation

The rear window demister system consist of the following components:

When you turn the ignition to the ON position, ignition voltage is supplied to the DEMIST relay coil. Battery positive voltage is supplied at all times to the DEMIST relay switched input. When the rear window demister switch is depressed, the HVAC control module illuminates the rear window demister indicator and sends a class 2 message to the BCM. The BCM energises the DEMIST relay by grounding the control circuit of the relay. This allows battery positive voltage from the relay switched input through the switch contacts and out the relay switched output to the rear window demister.

When you turn ON the ignition and press the rear window demister switch for the first time, the demister cycle lasts 10 minutes. Further operation results in 5 minute demister cycles.