GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

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

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Go to Step 2

Go to Symptoms

2

Turn ON the ignition switch.

With the rear defogger switch in the OFF position does the rear defogger grid turn off?

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

Go to Step 3

3

  1. Turn the ignition switch OFF.
  2. Disconnect the Heater-A/C and Rear Defogger Control Assembly connector.
  3. Measure the voltage between the rear defog element supply voltage circuit at the Heater-A/C and Rear Defogger Control Assembly connector and ground.

Is the measured voltage less than or equal to the specified value?

0 v

Go to Step 4

Go to Step 5

4

Replace the Heater-A/C and Rear Defogger Control Assembly.

Is the repair complete?

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Go to Step 6

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5

Locate and repair a short to voltage in the rear defog element supply voltage circuit.

Is the repair complete?

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Go to Step 6

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6

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 3