GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: Control head illumination/display does not operate properly.

1

Did you perform the HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2

  1. Turn ON the ignition, with the engine OFF.
  2. Press each button on the HVAC control module.

Do all the HVAC control module segments illuminate?

Go to Step 3

Go to Step 6

3

Do all other vehicle VF displays illuminate?

Go to Step 4

Go to Symptoms - Lighting Systems in Lighting Systems

4

  1. Cover the ambient light sensor.
  2. Turn ON the lights.

Does backlighting occur?

Go to Step 5

Go to Symptoms - Lighting Systems in Lighting Systems

5

Adjust the dimming control from minimum to maximum intensity.

Does the VF display increase and decrease in intensity?

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

Go to Step 6

6

Inspect for poor connections at the harness connector of the HVAC control module. 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 8

Go to Step 7

7

Replace the HVAC control module. Refer to HVAC Control Module Replacement .

Did you complete the replacement?

Go to Step 8

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8

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2