Normal Operation

The rear window defrost relay receives power from the Battery Junction Box (BJB) fuse 35 (10A) on circuit CBB35 (YE/GY). When the rear window defrost switch is pressed to the ON position, the HVAC module activates the rear window defrost relay by grounding circuit CH122 (WH/OG). When activated, the rear window defrost relay supplies 12 volts to the rear window defrost grid on circuit CRD06 (BN/YE). The rear window defrost grid is grounded through circuit GD149 (BK/GY).

The HVAC module will deactivate the rear window defrost relay when one of the following conditions is met:

• The rear window defrost switch is pressed when the feature is active.
• The ignition switch state is changed from ON to OFF/LOCK.
• The 15-minute timing function is complete.

For Escape Hybrid equipped with navigation only, the rear window defrost switch is integral to the Front Controls Interface Module (FCIM). When the defrost switch 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.

This pinpoint test is intended to diagnose the following: 

• Fuse
• Wiring, terminals or connectors
• Rear window defrost relay
• Rear window defrost switch (integral to the HVAC module)
• Rear window defrost grid
• HVAC module
• FCIM