GM Service Manual Online
For 1990-2009 cars only

Step

Action

Values

Yes

No

1

Did you perform the HVAC Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2

  1. Remove the automatic temperature controller (ATC) from the instrument panel (I/P), keeping the wiring harness connected.
  2. Turn ON the ignition, with the engine OFF.
  3. Turn the alternating current A/C switch to ON.
  4. Inspect the voltage between ground and terminal A11 on the controller.

Is the voltage within the specified value?

11-14 V

Go to Too Hot in Vehicle or Too Cold in Vehicle

Go to Step 3

3

Replace the ATC. Refer to Heater and Air Conditioning Control Replacement .

Is the repair complete?

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System OK

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