GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you review the HVAC operation and perform the necessary inspections?

--

Go to Step 2

Go to Symptoms

2

  1. Turn ON the ignition, with the engine OFF.
  2. Move the temperature control knob from extreme cold to extreme hot one step at a time.
  3. Monitor the temperature control door driving shaft on the back of the temperature control actuator while moving the temperature control knob. Refer to Temperature Actuator Replacement in Heating, Ventilation, and Air Conditioning.

Does the shaft move with every knob step movement?

--

Go to Step 3

Go to Step 4

3

  1. The problem is not electrical.
  2. Ensure that the vehicle is reaching the normal operating temperature.
  3. With a scan tool, observe the engine coolant temperature.

Is the vehicle reaching the normal operating temperature?

--

Go to Step 5

Go to Thermostat Diagnosis in Engine Cooling

4

Using a test lamp backprobe the temperature control actuator cavity 10 to ground.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 7

5

Inspect the temperature control door mechanical condition for binding. Refer to Temperature Actuator Replacement in Heating, Ventilation, and Air Conditioning.

Does any binding exist?

--

Go to Step 16

Go to Step 17

6

  1. Disconnect the temperature control actuator.
  2. Connect a test lamp between the temperature control actuator connector CKT 1050 (BLK) cavity 7 and CKT 141 (BRN) cavity 10.

Does the test lamp illuminate?

--

Go to Step 8

Go to Step 9

7

Repair the open in CKT 141 (BRN).

Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

8

  1. Disconnect the control assembly. Refer to Control Assembly Replacement in Heating, Ventilation, and Air Conditioning.
  2. Connector an ohmmeter between CKT 1050 (BLK) cavity B at the control assembly connector C3 to ground.

Does the resistance measure less than the specified value?

10 ohms

Go to Step 10

Go to Step 11

9

Repair the open in CKT 1050 (BLK).

Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

10

  1. Connect an ohmmeter between the control assembly connector C3 pin B and connector C2 pin F.
  2. Move the temperature control knob from extreme cold to extreme hot.

Does the resistance vary within the specified range?

0-10 Kohms

Go to Step 12

Go to Step 13

11

Repair the open in CKT 1050 (BLK).

Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

12

Using an ohmmeter measure the resistance from the control assembly connector C2 CKT 733 (LT BLU) cavity F and the temperature control actuator connector CKT 733 (LT BLU) cavity 8.

Does the resistance measure less than the specified value?

10 ohms

Go to Step 14

Go to Step 15

13

Replace the control assembly.

Refer to Control Assembly Replacement in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

--

Go to Step 18

--

14

Replace the temperature control actuator.

Refer to Temperature Actuator Replacement in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

--

Go to Step 18

--

15

Repair the open in CKT 733 (LT BLU).

Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

16

Repair the cause of the binding. Refer to Floor Air Outlet Replacement - Right Side in Heating, Ventilation, and Air Conditioning.

Did you complete the repair?

--

Go to Step 18

--

17

Repair restriction in coolant flow. Refer to Thermostat Diagnosis in Engine Cooling.

Did you complete the repair?

--

Go to Step 18

--

18

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2