GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Were you sent here by the Symptoms Table?

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Go to Step 2

Go to Symptoms

2

  1. Disconnect the rear window defogger relay.
  2. Turn the ignition switch to the RUN position.
  3. Use a test lamp to probe between B+ and the rear window defogger relay connector terminal A1 (CKT 292).

Does the test lamp light?

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Go to Step 5

Go to Step 3

3

Use a test lamp to probe between the rear window defogger relay connector terminal C 1 (CKT 293) and ground.

Does the test lamp light?

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Go to Step 8

Go to Step 4

4

Replace the rear window defogger relay.

Is the repair complete?

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Go to Step 9

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5

Inspect for a short to ground in CKT 292 (LT BLU). Refer to Testing for Short to Ground in Wiring Systems.

Did you find a short to ground on the circuit?

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Go to Step 6

Go to Step 7

6

Locate and repair the short to ground in CKT 292 (LT BLU). Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

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Go to Step 9

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7

Replace the heater-A/C control. Refer to one of the following procedures:

    •  Control Assembly Replacement for the manual HVAC system
    •  Control Assembly Replacement for the Automatic HVAC system

Is the repair complete?

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Go to Step 9

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8

Locate and repair a short to B+ in CKT 293 (PPL).

Is the repair complete?

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Go to Step 9

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9

Verify that the system operates properly.

Does the system operate properly?

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System OK

Go to Symptoms