Normal Operation
WARNING: This page is about a different car, the 2010 Mercury Milan, 2010 Lincoln MKZ, and 2010 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.
When the engine is running and the defrost switch (integral to the Front Controls Interface Module (FCIM)) is pressed, the FCIM sends the defrost request message to the HVAC module over the Controller Area Network (CAN). When the request is received, the HVAC module activates the rear window defrost relay by grounding the rear window defrost relay coil through circuit CH122 (WH/OG). When the rear window defrost relay is activated, power is supplied from the relay through the antenna module to the rear window defrost grid through circuit CRD06 (BN/YE)
- DTC B1C83:12 (Rear Defog Relay: Circuit Short to Battery) - When the HVAC module senses a short to voltage on the rear window defrost relay control circuit, this DTC will set.
- DTC B1C83:14 (Rear Defog Relay: Circuit Short to Ground or Open) - When the HVAC module senses an open or short to ground on the rear window defrost relay control circuit, this DTC will set.
This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Rear window defrost relay
- Wiring, terminals or connectors
- HVAC module
- FCIM
- Antenna module
- Rear window defrost grid