GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

1

Is the heater outlet duct air too warm?

Go to Step 2

Go to Step 5

2

  1. Turn the ignition switch ON.
  2. Move the temperature control from FULL COLD to FULL HOT.
  3. Listen for the temperature valve operation.

Is there a temperature valve operation?

Go to Step 3

Go to Step 4

3

  1. Verify that the valve operates properly.
  2. Inspect the system for binding or a disconnected actuator.

Did you find and repair the condition?

System OK

Go to Step 4

4

Inspect the temperature valve actuator for proper operation. Refer to Temperature Actuator Inoperative in HVAC Systems - Manual.

Is the repair complete?

System OK

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5

Is the air temperature in the vehicle too warm?

Go to Step 6

--

6

Inspect for air leaking out of the HVAC module heater case.

Is there air leaking out of the heater case?

Go to Step 7

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7

  1. Remove the HVAC module. Refer to HVAC Module Assembly Replacement .
  2. Inspect the module for the following:
  3. • Bad case seals
    • Broken case
    • Valves binding
    • Valves not sealing

Did you find and repair the condition?

System OK

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