Rear Defogger Switch: Testing and Inspection

WARNING: ON VEHICLES EQUIPPED WITH AIR-BAGS, DISABLE THE AIRBAG SYSTEM BEFORE ATTEMPTING ANY STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENT DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE THE BATTERY NEGATIVE (GROUND) CABLE, THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM CAPACITOR TO DISCHARGE BEFORE PERFORMING FURTHER DIAGNOSIS OR SERVICE. THIS IS THE ONLY SURE WAY TO DISABLE THE AIRBAG SYSTEM. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN AN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY.

NOTE: The rear window defogger switch may be tested in the vehicle or out of the vehicle, on a bench.

For rear window defogger switch circuit descriptions and diagrams, refer to Appropriate Wiring Information.

IN-VEHICLE TESTING
1. Remove the rear window defogger switch from the instrument panel, but leave the switch connected.
2. Turn the ignition switch ON.

Rear Window Defogger Switch Harness Connector:

3. Using a voltmeter, check for battery voltage at Pin 1 and 2 of the rear window defogger switch.
a. If OK, go to Step 4.
b. If NOT OK, check the 10 Amp fuse 6 in the fuse block and the 40 Amp fuse 8 in the Power Distribution Center (PDC). If fuses are OK, check wiring circuit. Refer to Wiring Diagrams.

4. Check Pin 5, with switch in the ON position there should be battery voltage and no voltage in the OFF position.
a. If OK, goto Step 5.
b. If NOT OK, no voltage in the ON position or voltage in the OFF position. Replace the switch.

5. Press switch to ON position. The indicator lamp should come on and remain on for approximately 10 minutes. If the indicator lamp fails to light or no voltage is present, replace the rear window defogger switch.

BENCH TESTING
1. Remove the rear window defogger switch.

Rear Window Defogger Switch Connector:

2. With switch removed from vehicle, use a jumper wire and connect a 12 volt supply to Pin 1 and 2. Using a third jumper wire, ground Pin 3. Refer to the Rear Window Defogger Switch and Harness Connector Pin Call-Out table.