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Makes 🢒 GMC_Truck 🢒 2003 🢒 Yukon - 4WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Too Cold in Vehicle - Auxiliary

Too Cold in Vehicle - Auxiliary With Heat and A/C

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step ensures that the primary HVAC system is functioning properly.

    2.

  2. If the condition does not occur when a heating request has been made then you must bypass the A/C compressor and cooling system diagnostic information.

    3.

  3. This step ensures that the rear auxiliary HVAC control module is able to move the auxiliary air temperature actuator.

    4.

  4. This step ensures that the front auxiliary HVAC control assembly is able to move the auxiliary air temperature actuator.

    5.

  5. There is 2 ignition 3 voltage circuits for the rear HVAC control assembly. The circuit that needs to be tested is the circuit that supplies ignition 3 voltage to the auxiliary HVAC control processor. If this circuit is open the auxiliary mode and air temperature actuators will not move with in there full range of motion.

  6. There is 2 ignition 3 voltage circuits for the rear HVAC control assembly. The circuit that needs to be tested is wired between the left I/P fuse block and the rear HVAC control assembly.

    7.

  7. The circuit that is to be tested is wired between the rear auxiliary HVAC control assembly and the auxiliary HVAC control processor. The circuit is the position signal from the rear auxiliary HVAC control assembly for the auxiliary air temperature actuator. The circuit only provides a reference when the front auxiliary HVAC control assembly is in the AUX position.

    8.

  8. The circuit that is to be tested is wired between the front auxiliary HVAC control assembly and the auxiliary HVAC control processor. The circuit is the position signal from the rear auxiliary HVAC control assembly for the auxiliary air temperature actuator. The circuit only provides a reference when the front auxiliary HVAC control assembly is in any other position than AUX position.

    9.

  9. This step checks the output of the auxiliary HVAC control processor to the auxiliary air temperature actuator.

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

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

1

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

--

Go to Step 2

Go to Symptoms - HVAC Systems - Manual

2

Important:: The auxiliary HVAC control assembly operates independently of the HVAC control module to provide heated airflow through the auxiliary system.

Does the HVAC control module operate and provide sufficient heating?

--

Go to Step 3

Go to Too Cold in Vehicle

3
  1. Turn ON the ignition, with the engine OFF.
  2. Place the front auxiliary blower motor switch in each speed position.

Does the auxiliary blower motor operate at all?

--

Go to Step 4

Go to Auxiliary Blower Motor Inoperative

4

Does the auxiliary blower motor operate at the desired speed in each speed position?

--

Go to Step 5

Go to Auxiliary Blower Motor Malfunction

5

Inspect the cooling system for the following conditions:

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

Did you find and correct the condition?

--

Go to Step 32

Go to Step 6

6
  1. Start the engine.
  2. Place the blower motor switch in the OFF position.
  3. Place the A/C request switch in the OFF position.

Does the A/C compressor operate?

--

Go to HVAC Compressor Clutch Does Not Disengage

Go to Step 7

7

  1. Turn ON the ignition, with the engine OFF.
  2. Select AUX on the front auxiliary HVAC control assembly.
  3. Observe the drive shaft of the auxiliary air temperature actuator.
  4. Adjust the rear auxiliary air temperature switch.

Does the auxiliary air temperature actuator drive shaft rotate at all?

--

Go to Step 8

Go to Step 11

8

  1. Place the front auxiliary blower motor switch in any position other than AUX on the front auxiliary HVAC control assembly.
  2. Place the front auxiliary air temperature switch from the coldest to hottest position.

Does the auxiliary air temperature actuator drive shaft rotate at all?

--

Go to Step 9

Go to Step 15

9

Test the ignition 3 voltage circuit that is wired between the rear auxiliary HVAC control assembly to the auxiliary HVAC control processor for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 32

Go to Step 10

10

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

    • Misaligned auxiliary air temperature actuator. Refer to Auxiliary Temperature Valve Actuator Replacement .
    • Broken or binding linkages or auxiliary air temperature door
    • Obstruction that prevents the auxiliary air temperature door from operating within it's full range of motion
    • Missing seals to the auxiliary air temperature door
    • Misaligned seals to the auxiliary air temperature door

Did you find and correct the condition?

--

Go to Step 32

Go to Heating Performance Diagnostic

11
  1. Place the front auxiliary blower motor switch in any position other than AUX on the front auxiliary HVAC control assembly.
  2. Place the front auxiliary air temperature switch from the coldest to hottest position.

Does the auxiliary air temperature actuator drive shaft rotate at all?

--

Go to Step 13

Go to Step 12

12

Test the ignition 3 voltage circuit of the rear auxiliary HVAC control assembly for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 32

Go to Step 18

13

Test the rear auxiliary temperature door control circuit of the rear auxiliary HVAC control assembly for an open, high resistance, a 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 32

Go to Step 14

14

Important:: The rear auxiliary HVAC control assembly connector must be connected to correctly perform test.

  1. Turn ON the ignition, with the engine OFF.
  2. Measure the voltage from the rear auxiliary temperature door control circuit of the rear auxiliary HVAC control assembly to a good ground.
  3. Place the front auxiliary air temperature switch from the coldest to hottest position.

Does the voltage change and measure within the specified range?

0-12 V

Go to Step 27

Go to Step 25

15

Test the ignition 3 voltage circuit of the front auxiliary HVAC control assembly 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 32

Go to Step 16

16

Test the auxiliary air temperature door position signal circuit of the front auxiliary HVAC control assembly for an open, high resistance, a 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 32

Go to Step 17

17

Important:: The front auxiliary HVAC control assembly connector must be connected to correctly perform test.

  1. Turn ON the ignition, with the engine OFF.
  2. Measure the voltage from the auxiliary air temperature door position signal circuit of the front auxiliary HVAC control assembly to a good ground.
  3. Place the front auxiliary air temperature switch from the coldest to hottest position.

Does the voltage change and measure within the specified range?

0-12 V

Go to Step 27

Go to Step 26

18

Test the ignition 3 voltage circuit of the auxiliary HVAC control processor 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 32

Go to Step 19

19

Test the ignition 3 voltage circuit of the auxiliary 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 32

Go to Step 20

20

Test the ground circuit of the auxiliary 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 32

Go to Step 21

21

Test the auxiliary air temperature door control circuit of the auxiliary air temperature actuator for an open, high resistance, a 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 32

Go to Step 22

22

Important:: The auxiliary HVAC control processor, front and rear auxiliary HVAC control assembly connectors must be connected to correctly perform test.

  1. Turn ON the ignition, with the engine OFF.
  2. Place the front auxiliary blower motor switch in any position other than AUX on the front auxiliary HVAC control assembly.
  3. Measure the voltage from the auxiliary air temperature door control circuit of the auxiliary air temperature actuator to a good ground.
  4. Place the front auxiliary air temperature switch from the coldest to hottest position.

Does the voltage change and measure within the specified range?

0-12 V

Go to Step 23

Go to Step 27

23

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 32

Go to Step 24

24

Inspect the auxiliary 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 32

Go to Step 28

25

Inspect for poor connections at the harness connector of the rear auxiliary HVAC control assembly. 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 32

Go to Step 29

26

Inspect for poor connections at the harness connector of the front auxiliary HVAC control assembly. 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 32

Go to Step 30

27

Inspect for poor connections at the harness connector of the auxiliary HVAC control processor. 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 32

Go to Step 31

28

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

Did you complete the replacement?

--

Go to Step 32

--

29

Replace the rear auxiliary HVAC control assembly. Refer to Auxiliary Heater and Air Conditioning Control Replacement - Rear .

Did you complete the replacement?

--

Go to Step 32

--

30

Replace the front auxiliary HVAC control assembly. Refer to Auxiliary Heater and Air Conditioning Control Replacement - Front .

Did you complete the replacement?

--

Go to Step 32

--

31

Replace the auxiliary HVAC control processor. Refer to Auxiliary HVAC Control Processor Replacement .

Did you complete the replacement?

--

Go to Step 32

--

32

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2

Too Cold in Vehicle - Auxiliary A/C Only

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step ensures that the primary HVAC system is functioning properly.

    2.

  2. If the condition does not occur when a heating request has been made then you must bypass the A/C compressor and cooling system diagnostic information.

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

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

1

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

--

Go to Step 2

Go to Symptoms - HVAC Systems - Manual

2

Important:: The auxiliary HVAC control assembly operates independently of the HVAC control module to provide heated airflow through the auxiliary system.

Does the HVAC control module operate and provide sufficient heating?

--

Go to Step 3

Go to Too Cold in Vehicle

3
  1. Turn ON the ignition, with the engine OFF.
  2. Select AUX on the front auxiliary HVAC control assembly.
  3. Place the A/C auxiliary blower motor switch in each speed position.

Does the auxiliary blower motor operate at all?

--

Go to Step 4

Go to Auxiliary Blower Motor Inoperative

4

Does the auxiliary blower motor operate at the desired speed in each speed position?

--

Go to Step 5

Go to Auxiliary Blower Motor Malfunction

5

Inspect the cooling system for the following conditions:

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

Did you find and correct the condition?

--

Go to Step 7

Go to Step 6

6
  1. Start the engine.
  2. Place the blower motor switch in the OFF position.
  3. Place the A/C request switch in the OFF position.

Does the A/C compressor operate?

--

Go to HVAC Compressor Clutch Does Not Disengage

Go to Step 7

7

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2