Window Defogger System Control Test

1. Stop the engine.
2. Check the fuse supplying power to the rear glass grid relay. If the fuse is good, (Refer to REAR WINDOW DEFOGGER RELAY - DIAGNOSIS AND TESTING). If the fuse is open, then go to Step 3.
3. Locate the ground lug that connects the negative lead of the rear window grid to ground. Remove the screw holding the ground lug and isolate it from any vehicle ground.
4. Connect one lead of an ohmmeter to the negative ground lug of the rear window grid (with the lug still not connected to a vehicle ground), and check the resistance to a known good vehicle ground. If the ohmmeter indicates less than 10 ohms, then the rear window defogger grid is shorting to the vehicle ground then go to Step 5. If the ohmmeter indicates more than 100 ohms of resistance, then go to Step 6.
5. Disconnect the rear window defogger grid voltage feed wire from the vehicle harness. If the ohmmeter still indicates less than 10 ohms, then the rear window defogger grid is shorting to the vehicle ground, then go to Step 5. If the ohmmeter indicates more than 100 ohms of resistance, then go to Step 6.
6. There is a problem with the circuits that connect to the rear window defogger relay. Check wiring with an ohmmeter to verify proper wiring connections to the rear window defogger relay. If no problems are found, then replace the fuse and try running the system.