GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Acadia - 2WD 🢒 HVAC 🢒 HVAC - Manual 🢒 Too Hot in Vehicle - Auxiliary

Test Description

The numbers below refer to the step numbers 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 control signal communication between the front and auxiliary HVAC control module.

    5.

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

    6.

  6. The value will vary between 0-255 counts 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 value will vary between 0-255 counts 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.

    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 auxiliary control.

    9.

  9. The value will vary between 0-255 counts during normal operation. The 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 cannot be adjusted from the auxiliary controls or the auxiliary heating is insufficient.

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

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

The auxiliary HVAC control module cannot request A/C compressor operation. An A/C request must be generated by the HVAC control module to provide cooled airflow through the auxiliary system.

Does the HVAC control module operate and provide sufficient heating?

--

Go to Step 3

Go to Diagnostic Starting Point - Heating, Ventilation and Air Conditioning

3
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the DTC List in Vehicle DTC Information.

Does the scan tool display any DTC B0423, B0433, or B3779?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 4

4
  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 work in each speed position.

Does the auxiliary blower motor operate at all?

--

Go to Step 5

Go to Auxiliary Blower Motor Malfunction

5

Does the auxiliary blower motor operate in each speed position?

--

Go to Step 6

Go to Auxiliary Blower Motor Malfunction

6
  1. Start the engine.
  2. Place the blower motor switch in the maximum speed position.
  3. Place the mode switch in the Vent position.
  4. Press the A/C request switch.
  5. Place the temperature switch in the coldest position.

Does the A/C compressor operate?

--

Go to Step 7

Go to Air Conditioning Compressor Malfunction

7

Perform the A/C System performance test. Refer to Air Conditioning (A/C) System Performance Test .

Did you find and correct the condition?

--

Go to Step 35

Go to Step 8

8

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

--

Go to Step 11

Go to Step 9

9

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

--

Go to Step 15

Go to Step 10

10

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

--

Go to Step 17

Go to Too Hot in Vehicle

11

  1. Install a scan tool.
  2. Set the front HVAC Auxiliary Blower motor control switch to any setting except AUX or OFF.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the AUX Temp Door Motor Position.
  5. Place the front air temp switch from the coldest to the warmest position.

Does the value measured stay within the specified range with a smooth transition between cold and hot?

0-255 Counts

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 12

12

  1. Install a scan tool.
  2. Set the front HVAC auxiliary blower motor switch control to any setting except Auxiliary or OFF.
  3. Disconnect the auxiliary air temperature actuator.
  4. Turn ON the ignition, with the engine OFF.
  5. Observe the Auxiliary Temp Door Motor Command.
  6. Place the front air temperature switch from the coldest position to the warmest position.

Does the value measured stay within the specified range with a smooth transition between COLD and HOT?

0-255 Counts

Go to Step 13

Go to Step 22

13

Connect a test light between the auxiliary air temperature actuator door A and B control circuits and the ground circuit of the auxiliary air temperature actuator.

Does the test light illuminate?

--

Go to Step 21

Go to Step 14

14

Connect a test light between the auxiliary air temperature actuator door A and B control circuits and a good ground.

Does the test light illuminate?

--

Go to Step 23

Go to Step 24

15

  1. Install a scan tool.
  2. Set the front HVAC auxiliary control blower motor switch to any setting except Auxiliary or OFF.
  3. Disconnect the auxiliary HVAC control.
  4. Turn ON the ignition, with the engine OFF.
  5. Observe the Auxiliary Temp Door Motor Command.
  6. Place the front air temperature switch from the coldest position to the warmest position.

Does the value measured stay within the specified range with a smooth transition between COLD and HOT?

0-255 Counts

Go to Step 16

Go to Step 26

16

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

Does the test lamp illuminate?

--

Go to Step 25

Go to Step 18

17

Connect a test lamp between the ignition 1 voltage circuit of the front HVAC control module and a good ground .

Does the test lamp illuminate?

--

Go to Step 30

Go to Step 26

18

  1. Install a scan tool.
  2. With a scan tool observe the Auxiliary Temp Door Motor Command.
  3. Disconnect the auxiliary HVAC control module.
  4. Place the front auxiliary blower motor switch to the Auxiliary control position.
  5. Place the auxiliary air temperature switch from the coldest position to the warmest position.

Does the value measure within the specified range with a smooth transition between COLD and HOT?

0-255 Counts

Go to Step 19

Go to Step 26

19
  1. Place the front auxiliary blower motor switch to the auxiliary control position.
  2. Connect a test lamp between the ignition 3 voltage circuit of the HVAC control module and the auxiliary blower motor control circuit of the front HVAC control module.

Does the test lamp illuminate?

--

Go to Step 26

Go to Step 20

20

Connect test lamp between the ignition 3 voltage circuit of the auxiliary blower motor and a good ground.

Does the test lamp illuminate?

--

Go to Step 25

Go to Step 28

21

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

    • An incorrectly installed auxiliary air temperature actuator--Refer to Auxiliary Temperature Valve 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 35

Go to Step 29

22

Test the auxiliary air temperature door control A and B circuits of the auxiliary air temperature actuator from the HVAC control module to the auxiliary air temperature actuator for the following conditions:

    • An open
    • 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 35

Go to Step 25

23

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

Did you find and correct the condition?

--

Go to Step 35

Go to Step 29

24

Test the auxiliary air temperature door 5 volt reference circuit of the auxiliary air temperature actuator from the HVAC control module to the auxiliary HVAC control module for the following conditions:

    • An open
    • 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 35

Go to Step 30

25

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

Did you find and correct the condition?

--

Go to Step 35

Go to Step 28

26

Test the auxiliary air temperature actuator 5 volt reference circuit for the following:

    • An open
    • 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 35

Go to Step 28

27

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

Did you find and correct the condition?

--

Go to Step 35

Go to Step 30

28

Test the ignition 3 voltage circuit of the auxiliary blower motor for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 35

Go to Step 30

29

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 .

Did you find and correct the condition?

--

Go to Step 35

Go to Step 32

30

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 35

Go to Step 33

31

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 .

Did you find and correct the condition?

--

Go to Step 35

Go to Step 34

32

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

Did you complete the replacement?

--

Go to Step 35

--

33

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

Did you complete the replacement?

--

Go to Step 35

--

34

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

Did you complete the replacement?

--

Go to Step 35

--

35

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2