GM Service Manual Online
For 1990-2009 cars only

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: The temperature cannot be adjusted, or the heating is insufficient.

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Turn ON the ignition, with the engine OFF.
  2. Place the blower control in each speed position.

Does the blower motor operate in any of the speed positions?

--

Go to Step 3

Go to Blower Motor Inoperative

3

Does the blower motor operate at the desired speed?

--

Go to Step 4

Go to Blower Motor Malfunction

4

  1. Start the engine.
  2. Turn OFF the HVAC controls.

Does the A/C compressor operate?

--

Go to HVAC Compressor Clutch Does Not Disengage

Go to Step 5

5

Inspect the cooling system for the following conditions:

    • A low coolant level
    • A loose or worn accessory drive belt
    • A leaking radiator hose or heater hose
    • A kinked radiator hose or heater hose
    • A missing radiator cap pressure seal
    • A leaking radiator cap

Did you find and correct the condition?

--

Go to Step 18

Go to Step 6

6

Perform the Heating Performance Diagnostic. Refer to Heating Performance Diagnostic in Heating, Ventilation and Air Conditioning.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 7

7

  1. Turn ON the ignition, with the engine OFF.
  2. Observe the drive shaft of the air temperature actuator.
  3. Place the air temperature switch from the coldest position to the warmest position.

Does the drive shaft of the air temperature actuator rotate?

--

Go to Step 8

Go to Step 9

8

Inspect the air temperature door and the air temperature actuator for the following conditions:

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

Did you find and correct the condition?

--

Go to Step 18

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

9

Test the ignition 3 voltage circuit of the air temperature actuator for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 10

10

Test the low reference circuit of the air temperature actuator for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 11

11

Test the control circuit of the air temperature actuator for an open, high resistance, short to ground, or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 12

12

Important: Ensure that the HVAC control module connector is connected during this step in order to avoid misdiagnosis.

  1. Turn ON the ignition, with the engine OFF.
  2. Measure the voltage from the air temperature door control circuit of the air temperature actuator to a good ground.
  3. Place the air temperature switch from the coldest position to the warmest position.

Does the voltage measure within the specified values with a smooth transition between cold and hot?

0 V at cold 12 V at hot

Go to Step 13

Go to Step 15

13

Inspect for poor connections at the harness connector of the air temperature actuator. 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 18

Go to Step 14

14

Inspect the air temperature actuator, door, and any attaching linkage for binding or a condition that prevents drive shaft rotation.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 16

15

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 18

Go to Step 17

16

Replace the air temperature actuator. Refer to Air Temperature Actuator Replacement .

Did you complete the replacement?

--

Go to Step 18

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17

Replace the HVAC control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 18

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18

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 2