Rear Window Defogger

See also our discussion of the Rear Window Defogger.


  1. Remove the rear seat.
  2. Locate the rear window defogger switch in the dashboard. It will have a white wire running to it from Fuse #10, a black wire leading to the relay, and a brown ground wire.
  3. Confirm that the switch is wired properly.
  4. Trace the black wire from the switch back to the defogger relay under the back seat. There are five wires on the relay:
    • The black wire from the defogger switch.
    • A black wire that leads to an in-line fuse (8 amp).
    • A brown ground wire.
    • A blue/white wire to the analysis system.
    • A white wire to the defogger in the rear window.

  5. Confirm that all of these wires are in place and in decent shape and that the in-line fuse is in place.
  6. Turn on the key and the defogger switch and check the voltage at the point where the black wire from the switch connects to the relay. Should be 12 volts; if no voltage, the defogger switch is bad.
  7. If there is juice to the relay, check for voltage at the point where the black wire from the in-line fuse connects to the relay. There should also be 12 volts at this point.
  8. Check for voltage at the point where the white wire from the relay connects to the defogger grid. Should be 12 volts at this point also.
  9. If there is no voltage at any of the above test points, move upstream and correct or replace the faulty component.
  10. Turn off the defogger switch and the key.
  11. If you found voltage at the point where the hot wire attaches to the defogger grid, remove the wires on both sides of the grid and check for continuity across the grid. Also check each of the individual lines.
  12. If you have voltage to the defogger grid but no continuity across the grid, the grid will have to be repaired or replaced.


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