Rear Window Defrost

WARNING: This page is about a different car, the 2021 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

When the rear window defrost switch (integral to the HVAC module) is activated, the HVAC module sends the request message to the BCMC. The BCMC supplies voltage to the rear window defrost grid(s). In some cases, the rear window defrost system may automatically activate 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.

If equipped, the rear window defrost can also be commanded on and off using the rear window defrost button located on the touchscreen interface. For additional information on touchscreen commanded features, refer to the Owner's Literature.

The BCMC 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.
If equipped, the rear window defrost is commanded off using the touchscreen interface 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).