Express 1/2 Ton Van V8-305 5.0L VIN M SFI (1998)
Important:
The first part of the test must be completed quickly before the entire surface of the back window becomes warm.
3.1.1. From outside the vehicle, place the heat sensitive paper (dull surface in contact with the glass) against the top driver side 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 the bottom
grid lines until they have all been checked in the driver side zone.
3.1.2. Repeat the process for the passenger side and center area zones.
3.1.3. 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.
3.2.
Method using portable infrared thermometer:
3.2.1. Start the engine and turn on the rear back window defogger.
3.2.2. 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 district variation in temperature readings.
3.2.3. 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.
3.2.4. Repeat the process for the passenger side and center area zones.
4.
Use Permatex(R) Quick Grid, GM P/N 12346001, or equivalent, to repair each broken grid line. Follow the manufacturer's instructions.
5.
Wait 24 hours before turning the defogger on, or the repair can 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.
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