GM Service Manual Online
For 1990-2009 cars only

Step

Action

Normal Result(s)

Abnormal Result(s)*

1

Start the engine.

  1. The defogger ON indicator is OFF.
  2. The defogger is OFF.

2

  1. Press and release the defogger switch once.
  2. Wait approximately 11 minutes.
  1. The defogger ON indicator turns ON.
  2. The defogger turns ON.
  3. After approximately 10 minutes, both the defogger indicator and the defogger turns OFF.

3

  1. Press and release the defogger switch once.
  2. Wait approximately 6 minutes.
  1. The defogger ON indicator turns ON.
  2. The defogger turns ON.
  3. After approximately 5  minutes, both the defogger ON indicator and the defogger turn OFF.

4

  1. Press and release the defogger switch once.
  2. Wait approximately 15 seconds.
  3. Press and release the defogger switch a second time, before a time-out occurs.
  1. The defogger ON indicator turns ON.
  2. The defogger turns ON.
  3. After the switch is pressed a second time, both the defogger ON indicator and the defogger turn OFF immediately.

* Refer to the appropriate symptom diagnostic table for the applicable abnormal result.