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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 Montana - 4WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Too Hot in Vehicle - Auxiliary

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. The specified values are from the A/C System Performance Test.

    2.

  2. The functionality of the auxiliary air temperature drive shaft is questioned.

    3.

  3. The functionality of the auxiliary air temperature door control circuit of the auxiliary HVAC control module is questioned.

    4.

  4. This step questions the status of the air temperature door position signal communication between the front and auxiliary HVAC control modules.

    5.

  5. This step checks for proper auxiliary air temperature actuator drive shaft movement.

    6.

  6. The voltage will vary between 0.25-14.7 volts during normal operation. The HVAC control module connector must be connected during this step. This checks for proper operation of the air temperature actuator door control circuit and the HVAC control module.

    7.

  7. The voltage will vary between 0.25-14.7 volts during normal operation. The HVAC control module connector must be connected during this step. This checks for proper operation of the air temperature actuator door control circuit and the HVAC control.

    8.

  8. The auxiliary blower motor switch control circuit should not have continuity to ground when front auxiliary blower control switch is in any position except REAR CNTL.

    9.

  9. The voltage will vary between 0.25-14.7 volts during normal operation. The auxiliary HVAC control module connector must be connected during this step.

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: Auxiliary air temperature can not be adjusted from one or both auxiliary controls or auxiliary heating is insufficient.

This table diagnoses vehicles equipped with the auxiliary HVAC control module.

1

Did you perform the HVAC Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Manual

2
  1. Turn ON the ignition, with the engine OFF.
  2. Place the mode switch in any position except OFF.
  3. Place the auxiliary blower control in each speed position.

Does the auxiliary blower motor operate at all?

--

Go to Step 3

Go to Auxiliary Blower Motor Inoperative

3

Does the auxiliary blower motor operate in each speed position?

--

Go to Step 4

Go to Auxiliary Blower Motor Malfunction

4
  1. Start the engine.
  2. Place the blower motor switch in the maximum speed position.
  3. Place the mode switch in the Panel position.
  4. Turn A/C ON.
  5. Place the temperature switch in the coldest position.

Does the A/C compressor operate?

--

Go to Step 5

Go to HVAC Compressor Clutch Does Not Engage

5

Perform the A/C system performance test. Refer to Air Conditioning (A/C) System Performance Test in Heating, Ventilation and Air Conditioning.

Did you find and correct the condition?

--

Go to Step 34

Go to Step 6

6

Does the Auxiliary Too Hot in Vehicle condition happen only with the auxiliary HVAC control module?

--

Go to Step 9

Go to Step 7

7

Does the Auxiliary Too Hot in Vehicle condition occur only when using the front HVAC control module?

--

Go to Step 13

Go to Step 8

8

Does the Auxiliary Too Hot in Vehicle condition happen with both the front and auxiliary HVAC control modules?

--

Go to Step 16

Go to Too Hot in Vehicle

9

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

Does the auxiliary air temperature actuator move with a smooth transition between COLD and HOT?

--

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

Go to Step 10

10

  1. Disconnect the auxiliary air temperature actuator.
  2. Place the front auxiliary blower motor switch to any position except REAR CNTL or OFF.
  3. Place the front auxiliary air temperature switch from the coldest position to the warmest position.
  4. Measure the voltage of the auxiliary air temperature door control circuit between both HVAC modules of the auxiliary air temperature actuator to a good ground.

Does the voltage measure within the specified values with a smooth transition between COLD and HOT?

0.25-14.7 V

Go to Step 11

Go to Step 20

11

Connect a test lamp between the ignition 3 voltage circuit and the ground circuit of the auxiliary air temperature actuator.

Does the test lamp illuminate?

--

Go to Step 19

Go to Step 12

12

Connect a test lamp between the ignition 3 voltage circuit and a good ground.

Does the test lamp illuminate?

--

Go to Step 21

Go to Step 22

13

  1. Disconnect auxiliary HVAC control module.
  2. Place the front auxiliary blower motor switch to any position except REAR CNTL or OFF.
  3. Place the front auxiliary air temperature switch from the coldest position to the warmest position.
  4. Measure the voltage of the auxiliary air temperature door control circuit between both HVAC modules of the auxiliary HVAC control module to a good ground.

Does the voltage measure within the specified values with a smooth transition between COLD and HOT?

0.25-14.7 V

Go to Step 14

Go to Step 23

14

  1. Place the front auxiliary blower motor switch to any position except REAR CNTL or OFF.
  2. Connect a test lamp between the ignition 3 voltage circuit of the front HVAC control module and rear auxiliary blower motor switch control circuit of the HVAC control module.

Does the test lamp illuminate?

--

Go to Step 24

Go to Step 15

15

Connect a test lamp between the ignition 3 voltage circuit and a good ground .

Does the test lamp illuminate?

--

Go to Step 29

Go to Step 25

16

  1. Disconnect the auxiliary HVAC control module.
  2. Place the front auxiliary blower motor switch to the REAR CNTL position.
  3. Place the auxiliary air temperature switch from the coldest position to the warmest position. Monitor the actuator drive shaft for full rotation.
  4. Measure the voltage of the auxiliary air temperature door control circuit of the auxiliary HVAC control module to a good ground.

Does the voltage measure within the specified values with a smooth transition between COLD and HOT?

0.25-14.7 V

Go to Step 17

Go to Step 25

17
  1. Place the front auxiliary blower motor switch to the REAR CNTL position.
  2. Connect a test lamp between the ignition 3 voltage circuit of the auxiliary HVAC control module and the auxiliary blower motor control circuit of the front HVAC control module.

Does the test lamp illuminate?

--

Go to Step 25

Go to Step 18

18

Connect test lamp between the ignition 3 voltage circuit of the auxiliary HVAC control module and a good ground.

Does the test lamp illuminate?

--

Go to Step 26

Go to Step 27

19

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

    • An incorrectly installed auxiliary air temperature actuator
    • 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 34

Go to Step 28

20

Test the auxiliary air temperature door control circuit of the auxiliary air temperature actuator from the auxiliary HVAC control module to the auxiliary 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 34

Go to Step 25

21

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

Did you find and correct the condition?

--

Go to Step 34

Go to Step 28

22

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 34

Go to Step 28

23

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

Did you find and correct the condition?

--

Go to Step 34

Go to Step 29

24

Test the rear auxiliary blower motor control circuit for short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 34

Go to Step 29

25

Test the auxiliary air temperature position signal circuit between the auxiliary HVAC control module and the HVAC control module for an open, high resistance, short to ground, and short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 34

Go to Step 28

26

Test the rear auxiliary blower motor control circuit for an open or high resistance. Refer to Circuit Testing and in Wiring Repairs Wiring Systems.

Did you find and correct the condition?

--

Go to Step 34

Go to Step 30

27

Test the ignition 3 voltage circuit of the auxiliary HVAC control module 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 34

Go to Step 30

28

Inspect for poor connections at the harness connector of the auxiliary 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 34

Go to Step 31

29

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 34

Go to Step 32

30

Inspect for poor connections at the harness connector of the auxiliary 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 34

Go to Step 33

31

Replace the auxiliary air temperature actuator. Refer to Auxiliary Temperature Valve Actuator Replacement .

Did you complete the replacement?

--

Go to Step 34

--

32

Replace the HVAC control module. Refer to HVAC Control Module Replacement .

Did you complete the replacement?

--

Go to Step 34

--

33

Replace the auxiliary HVAC control module. Refer to Auxiliary Heater and Air Conditioning Control Module Replacement in HVAC Manual or VES Overhead Console Replacement in Entertainment Systems.

Did you complete the replacement?

--

Go to Step 34

--

34

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2