Rear Window Defogger Function Test

NOTE:
  • Be careful not to scratch or damage the defogger wires with the tester probe.
  • Before testing, check the No. 11 (20A) fuse in the under-hood fuse/relay box and No. 14 (10A) fuse in the under-dash fuse/relay box.

1.Check for voltage between the positive terminal (A) on the right side of the glass and body ground with the ignition switch and defogger switch ON.
There should be battery voltage.

  • If there is no voltage, check for:
    • faulty  defogger relay.
    • an open in the BLK/RED, BLK/YEL, or YEL/BLK wire.
    • faulty  the heater control panel or climate control unit.
  • If there is battery voltage, go to 2.

 

2.Check for voltage between the positive terminal (A) and the negative terminal (B).
If there is no voltage, check for:
  • an open in the BLK wire.
  • Poor ground (G601 or G701).

3.Touch the voltmeter positive probe to the halfway point of each defogger wire, and the negative probe to the negative terminal.
There should be about 6 V with the ignition switch and the defogger switch ON.

  • If the voltage is as specified, the defogger wire is OK.
  • If the voltage is not as specified, repair the defogger wire.
    • If there is battery voltage, there is a break in the negative half of the grid.
    • If it there is 0 V, there is a break in the positive half of the grid.