Rear Defogger Grid Inoperative or Incomplete Defogging of Rear Glass (Repair Broken Defogger Grid Wires)

This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 05-08-48-003A (Section 08 - Body & Accessories).

Some customers may comment that the rear defogger grid is inoperative or that the rear glass is not completely defogged (patches of fog or frost remain after rear defogger grid has been activated for several minutes).

The rear defogger grid may have broken defogger grid lines.

Check the rear defogger grid using the methods listed in this bulletin in order to diagnose inoperative or broken defogger grid lines. Repair any detected breaks using the procedure below.

Materials Required

Broken Defogger Line Diagnosis and Repair

To detect a broken grid line and to isolate the exact location of the break, perform the following:

Caution: Approved safety glasses and gloves should be worn when performing this procedure to reduce the chance of personal injury.

Notice: Cover the rear shelf area to prevent damage to the interior trim material.

1. Start the engine and turn on the back window defogger.
2. Take the ball of fine steel wool and twist one end to a point. Move the point slowly across each grid line. When you bridge the grid line break with the steel wool, you will see a small spark. Repeat the test over the same area to be sure you have accurately located the break. Mark the exact location of the grid line break. Repeat this portion of the test for each grid line. If you do not see a spark at any point, it is possible that there are two breaks in the same line. Close visual inspection using a magnifying glass may be the only way to locate breaks in this case.
3. The following methods are provided as alternative ways to detect a non-functional grid line. If available, use in addition to the steel wool.

Method using liquid crystal heat sensitive paper:

Important:  The first part of the test must be completed quickly before the entire surface of the back window becomes warm.

3.1.

From outside the vehicle, place the heat sensitive paper (dull surface in contact with the glass) against the top grid line. Start the engine and turn on the back window defogger. A distinct color change will take place at each conductive grid line. Repeat for each lower grid line until they have all been checked.

3.2.	If no color change is noted for a grid line, place a crayon or china marker check mark beside it. Mark each grid line in the zone where it is non-conductive and, therefore, not heating up. More than one broken grid line may be found.

Method using portable infrared thermometer:

3.1.	Start the engine and turn on the rear back window defogger.

3.2.	From inside the vehicle, start at the top driver side grid line and slowly run the portable infrared thermometer vertically down the rear window contacting each grid line. You should be able to see a distinct variation in temperature readings.

3.3.	Mark each grid line in the zone where it is non-conductive and, therefore, not heating up. More than one broken grid line may be found.

4. Use Permatex® Quick Grid, P/N 12346001, or equivalent, to repair each broken grid line. Follow the manufacturer's instructions for use of the repair kit.
5. Wait 24 hours before turning the defogger on. The repair can also be fast cured using a heat gun, 260°C-371°C (500°F-700°F). Hold the heat gun within 25-51 mm (1-2 in) from the repair point for 2 to 3 minutes.
6. Recheck the grid line with the heat sensitive paper or portable infrared thermometer to ensure that the line is now functional and that the repair was successful.

For vehicles repaired under warranty, use: