Normal Operation
WARNING: This page is about a different car, the 2013 Ford Mustang. 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). The HVAC module activates the rear window defrost relay by grounding the relay coil. When the rear window defrost relay is activated, power is supplied from the relay to the rear window defrost grid.
- DTC B1C83:11 (Rear Defog Relay: Circuit Short to Ground) - When the HVAC module senses a short to ground on the rear window defrost relay control circuit, this DTC will set.
- DTC B1C83:13 (Rear Defog Relay: Circuit Open) - When the HVAC module senses an open 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
- Rear window defrost grid
- HVAC module
- FCIM