The REAR DEFOG relay supplies voltage to the outside rearview mirror heater elements based on the current state of the rear window defogger. The relay supplies B+ through the driver/passenger mirror heating element control circuits when a request is seen.

Schematic Reference

Outside Rearview Mirror Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Outside Mirror Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, press the rear window defogger switch. Verify the rear window defogger turns ON and the rear window becomes warm.

⇒	If the rear window defogger does not turn on, refer to Rear Window Defogger Malfunction.

2. Verify both the left and right outside mirror glass become warm.

1. Ignition OFF, disconnect the harness connector at the appropriate outside rearview mirror.
2. Test for less than 10 ohms between the ground circuit terminal A and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance.

3. Connect a test lamp between the heater element control circuit terminal C and ground.
4. Ignition ON, operate the rear window defogger ON and OFF with the rear defogger switch. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance.

5. If all circuits test normal, test or replace the outside rearview mirror glass.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Outside Rearview Mirror Glass Replacement