Rear Window Defogger

Function Test


Defogger Wire Repair

  • Be careful not to scratch or damage the defogger wires with the tester probe.
  • Before testing, check the No. 11 (40 A) fuse in the under-hood fuse/relay box and No. 14 (10 A) fuse in the under-dash fuse/relay box.
  1. Check for voltage between the positive terminal (A) 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.
  • faulty antenna module.
  • an open in the wire between the defogger relay and positive terminal.
  • faulty defogger switch.
  1. Check for continuity between the negative terminal (B) and body ground.

If there is no continuity, check for:

  • an open in the BLK wire.
  • Poor body ground at the window antenna coil mounting bolt.
  • Poor ground (G701)
  1. 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 it is more than 6 V, there is a break in the negative half of the wire.
  • If it is less than 6 V, there is a break in the positive half of the wire.

NOTE: To make an effective repair, the broken section must be no longer than one inch.
  1. Lightly rub the area around the broken section (A) with fine steel wool, then clean it with alcohol.

  1. Carefully mask above and below the broken portion of the defogger wire (B) with transparent tape (C).
  2. Using a small brush, apply a heavy coat of silver conductive paint extending about 1/8" on both sides of the break. Allow 25 minutes to dry. Thoroughly mix the paint before use.

  1. Check for continuity in the repaired wire.
  2. Apply a second coat of paint in the same way. Let it dry 3 hours before removing the tape.