GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you review the Stationary Windows Description and perform the necessary inspections?

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Go to Step 2

Go to Symptoms

2

  1. Place the ignition switch in the RUN position.
  2. Turn ON the rear defogger switch.

Does the rear defogger indicator illuminate?

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Go to Step 3

Go to Defogger Indicator Inoperative

3

Use a test lamp in order to backprobe CKT 293 (PPL) at the HVAC control module connector C1 to ground.

Does the test lamp illuminate?

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Go to Step 5

Go to Step 4

4

Replace the HVAC control module. Refer to Control Assembly Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

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Go to Step 10

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5

  1. Disconnect the HVAC control module connector.
  2. Disconnect the rear window defogger power connector on the left side of the grid.
  3. Use an ohmmeter in order to inspect for continuity of CKT 293 (PPL) between the HVAC control module connector C1 and the left side of the defogger grid power connector.

Is there continuity between the components?

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Go to Step 7

Go to Step 6

6

Locate and repair an open or a short to ground in CKT 293 (PPL) between the HVAC control module connector and the rear defogger grid. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

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Go to Step 10

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7

  1. Disconnect the rear window defogger ground connector on the right side of the grid.
  2. Use an ohmmeter in order to inspect for continuity between the right side of the rear defogger grid ground connector and ground.

Is there continuity between the components?

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Go to Step 8

Go to Step 9

8

Repair the defogger grid(s) as needed.

Did you complete the repair?

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Go to Step 10

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9

Repair an open in the ground circuit between the rear defogger grid ground connector and G403. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

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Go to Step 10

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10

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 2