GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Defogger Schematics

Connector End View Reference: Stationary Windows Connector End Views

1

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

Go to Step 2

Go to Symptoms - Stationary Windows

2

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

Does the rear window defogger indicator turn ON and OFF with each command?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the RR DEOG relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Command the rear window defogger indicator ON and OFF, by depressing the rear window defogger switch.
  5. Observe the rear window defogger indicator on the HVAC Control Assembly.

Does the rear window defogger indicator turn ON and OFF with each command?

Go to Step 5

Go to Step 4

4

Test the control circuit of the RR DEFOG relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 9

Go to Step 6

5

Inspect for poor connections at the RR DEFOG relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 9

Go to Step 7

6

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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 9

Go to Step 8

7

Replace the RR DEFOG relay.

Did you complete the replacement?

Go to Step 9

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8

Replace the HVAC Control Assembly. Refer to Heater and Air Conditioning Control Replacement in HVAC Systems - Manual.

Did you complete the replacement?

Go to Step 9

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9

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2