Rear Window Defrost

The rear window defrost system only operates when the engine is running. When the rear window defrost switch is activated, the HVAC module sends the request message to the BCM. The BCM then sends the request through a LIN to the BJB, activating the rear window defrost relay (integral to the BJB). When the rear window defrost relay is activated, the rear window defrost grid(s) are energized. The rear window defrost system may also be automatically activated as an extra load for accelerated engine warm-up, however the rear window defrost status LED remains off unless the rear window defrost switch is activated.

The BCM deactivates the rear window defrost relay when one of these conditions is met:

• The rear window defrost switch is pressed when the feature is active.
• Ignition state is changed from ON to OFF.
• A predetermined timer completes.
• Battery voltage has dropped below a specified threshold (load management strategy).