Normal Operation
WARNING: This page is about a different car, the 2011 Mercury Milan, 2011 Lincoln MKZ, and 2011 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 which supplies voltage through the antenna module to the rear window defrost grid.
- DTC B1C83:12 (Rear Defog Relay: Circuit Short to Battery) - sets when the HVAC module detects a short to voltage on the rear window defrost relay control circuit.
- DTC B1C83:14 (Rear Defog Relay: Circuit Short to Ground or Open) - sets when the HVAC module detects an open or short to ground on the rear window defrost relay control circuit.
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