GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

1

Did you perform the function test?

Go to Step 2

Go to Function Test

2

  1. Set the mode control to the VENT position.
  2. Set the temperature control to the coldest position.
  3. Set the blower speed to HIGH.
  4. Inspect for airflow at the following outlets:
  5. • The vent
    • The heater
    • The defroster
    • The side window defroster

Do only the vent outlets have airflow at an ambient temperature?

Go to Step 3

Go to Step 5

3

  1. Set the mode control to the HEAT position.
  2. Set the temperature control to the hottest position.
  3. Verify the airflow at the following outlets:
  4. • The heater outlets have high airflow.
    • The defroster outlets have minimum airflow.
    • The side window defroster outlets have minimum airflow.
    • The vent outlets do not have airflow.

Is the air delivery correct?

Go to Step 4

Go to Step 5

4

  1. Set the mode control to the DEFROST position.
  2. Verify the airflow at the following outlets:
  3. • The defroster outlets have a high airflow.
    • The side window defroster outlets have minimum airflow.
    • The heater outlets have minimum airflow.
    • The vent outlets do not have airflow.

Is the air delivery correct?

Go to Function Test

Go to Step 5

5

  1. Disconnect the affected control cable at the heater case.
  2. Inspect the door travel and the door effort.

Are the door travel and the door effort OK?

Go to Step 6

Go to Step 8

6

Test the control cable travel by moving the corresponding control at the heater control unit.

Is the control cable travel correct?

Go to Step 7

Go to Step 9

7

  1. Inspect the control cable attachment at the heater control unit.
  2. Repair the control cable attachment, as necessary. Refer to Control Assembly Replacement .

Is the repair complete?

Go to Function Test

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8

Repair the affected door at the heater case. Refer to Heater Case Replacement .

Is the repair complete?

Go to Function Test

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9

Repair or replace the affected control cable as necessary. Refer to the following procedures:

    • Temperature Control Cable Replacement
    • Vent Control Cables Replacement

Is the repair complete?

Go to Function Test

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