GM Service Manual Online
For 1990-2009 cars only

Diagnostic Aids

    • The condition may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections .
    • Inspect the air delivery system for the following conditions:
       - An obstruction to the airflow
       - Air leaks
       - Misaligned air ducts
       - Broken or binding linkages or doors

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step drives the actuator in both directions. If the actuator door is already in the position you are attempting to drive it to, reverse the polarity to drive the actuator in opposite direction.

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: Air does not flow correctly from the air distribution outlets.

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Turn ON the ignition, with the engine OFF.
  2. Turn OFF the HVAC controls.

Is the blower motor OFF?

Go to Step 3

Go to Blower Motor Always On

3

Place the blower motor switch in each speed position.

Does the blower motor operate in each speed position?

Go to Step 4

Go to Blower Motor Inoperative

4

Does the blower motor operate at the desired speeds?

Go to Step 5

Go to Blower Motor Malfunction

5

Place the mode switch in each mode position.

Does the air flow from the correct air distribution outlets in each selected mode position?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 6

6

Test the mode door control A circuit and the mode door control B circuit for the following:

    •  An open
    •  A high resistance
    • A short to ground
    • A short to voltage

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 13

Go to Step 7

7

  1. Turn OFF the ignition.
  2. Disconnect the HVAC Control Module.
  3. Connect a 10-amp fused jumper wire between the actuator door control A circuit of the mode actuator and battery positive voltage.
  4. Connect a 10-amp fused jumper wire between the actuator door control B circuit of the mode actuator and a good ground.
  5. Reverse the polarity between the Mode actuator control A and B circuits.

Does the actuator shaft rotate in both directions?

Go to Step 8

Go to Step 9

8

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 .

Did you find and correct the condition?

Go to Step 13

Go to Step 12

9

Inspect the mode door and actuator for the following conditions:

    • A misaligned mode actuator--Refer to Mode Actuator Replacement .
    • Broken or binding linkages or actuator door
    • An obstruction that prevents the actuator door from operating within its full range of motion
    • Missing seals to the actuator door
    • Misaligned seals to the actuator door

Did you find and correct the condition?

Go to Step 13

Go to Step 10

10

Inspect for poor connections at the harness connector of the mode actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 13

Go to Step 11

11

Replace the mode actuator. Refer to Mode Actuator Replacement .

Did you complete the replacement?

Go to Step 13

--

12

Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 13

--

13

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3