GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Defogger Schematics

Connector End View Reference: Window Systems Connector End Views

1

Did you review the Rear Window Defogger system operation and perform the necessary inspections?

Go to Step 2

Go to Rear Window Defogger Description and Operation

2

  1. Turn ON the ignition, with the engine OFF.
  2. Observe the rear window defogger indicator on the HVAC control assembly.
  3. Command the rear window defogger indicator ON and OFF, by depressing the rear window defogger switch on the HVAC control assembly.

Does the indicator remain illuminated?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections

3

  1. Turn OFF the ignition.
  2. Disconnect the harness connector C1 of the HVAC control assembly.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the supply voltage circuit terminal D of the rear window defogger and a good ground.

Does the test lamp illuminate?

Go to Step 5

Go to Step 4

4

Inspect for poor connections at the harness connector of the HVAC control assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 7

Go to Step 6

5

Repair a short to voltage in the supply voltage circuit of the rear window defogger grid. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 7

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6

Replace the HVAC control assembly. Refer to Heater and Air Conditioning Control Replacement .

Did you complete the replacement?

Go to Step 7

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7

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2