Rear Window Defrost
WARNING: This page is about a different car, the 2012 Ford Pickup, 2012 Ford F550 Super Duty, 2012 Ford F450 Super Duty, and 2012 Ford Cab & Chassis. 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 pressed and the engine is running, the HVAC module activates the rear window defrost relay located in the Battery Junction Box (BJB). When the rear window defrost relay is active, the heated mirror and rear window defrost grids are energized.