GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Yukon XL - 2WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Too Hot in Vehicle

Test Description

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

  1. The HVAC control module is inoperative when the module does not respond to an operator control request.

    2.

  2. If the condition does not occur when an A/C request has been made then you must bypass the A/C performance test procedures.

    3.

  3. If the vehicle has poor A/C performance at idle then there could be an issue with the radiator air baffle assemblies or deflectors.

    4.

  4. These actions are the enable criteria for the A/C compressor to operate. Ambient air temperature must be above 3°C (38°F) in order for this A/C compressor test to be run.

    5.

  5. Performing the Air Conditioning System Performance Test ensures that the A/C system is operating properly for further testing.

    6.

  6. If no condition found with all conditions listed then compare door travel to known good vehicle.

    7.

  7. The voltage will vary between 0-5 volts during normal operation. Ensure to observe the air temperature actuator driveshaft and the volt meter when jumping the control circuit with 5 volt reference and the ground circuits. The air temperature actuator and the HVAC control assembly connectors must be connected during this step.

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: The temperature cannot be adjusted, or the cooling is insufficient during A/C operation.

1

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

--

Go to Step 2

Go to Symptoms - HVAC Systems - Manual

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

Does the blower motor operate at all?

--

Go to Step 3

Go to Blower Motor Inoperative

3

Does the blower motor operate correctly for each speed position?

--

Go to Step 4

Go to Blower Motor Malfunction

4

Is the HVAC control module inoperative?

--

Go to Step 19

Go to Step 5

5

Does the Too Hot in Vehicle concern occur when A/C cooling is desired?

--

Go to Step 6

Go to Step 9

6

Inspect the air baffles for proper installation. Refer to Radiator Air Baffle Assemblies and Deflectors in Engine Cooling.

Did you find and correct the condition?

--

Go to Step 26

Go to Step 7

7

Important:: For A/C compressor operation, ambient air temperature must be above 3°C (38°F).

  1. Start the engine.
  2. Place the blower motor switch in the maximum speed position.
  3. Place the A/C request switch in the ON position.
  4. Place the air temperature switch in the coldest position.

Does the A/C compressor operate?

--

Go to Step 8

Go to HVAC Compressor Clutch Does Not Engage

8

Perform the refrigerant 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 26

Go to Step 9

9
  1. Observe the drive shaft of the air temperature actuator.
  2. Adjust the air temperature switch.

Does the air temperature actuator drive shaft rotate at all?

--

Go to Step 10

Go to Step 11

10

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

    • Misaligned air temperature actuator. Refer to Air Temperature Actuator Replacement .
    • Broken or binding linkages or air temperature door
    • Obstruction that prevents the air temperature door from operating within it's 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 26

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

11

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 26

Go to Step 12

12

Test the ground 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 26

Go to Step 13

13

Test the 5-volt reference circuit of the air temperature actuator for an open, a 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 26

Go to Step 14

14

Test the air temperature position signal circuit of the air temperature door 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 26

Go to Step 15

15

Test the air temperature door 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 26

Go to Step 16

16

Important:: The air temperature actuator connector and the HVAC control module connector must be connected to correctly perform tests.

  1. Turn ON the ignition, with the engine OFF.
  2. Backprobe and monitor the voltage from the air temperature door position signal circuit of the air temperature actuator to a good ground.
  3. Connect a 3-ampere fused jumper wire between the air temperature door control circuit and the 5-volt reference circuit of the air temperature actuator. This action drives the actuator to the full COOL mode.
  4. Remove and reconnect the jumper wire between the air temperature door control circuit and the ground circuit of the air temperature actuator. This action drives the actuator to the full HOT mode.

Does the air temperature actuator drive shaft rotate and does the voltage change?

--

Go to Step 17

Go to Step 21

17
  1. Backprobe the air temperature actuator connector terminal in order to measure the voltage from the air temperature door control circuit to a good ground.
  2. Adjust the air temperature switch.

Does the voltage measure near the specified value when increasing air temperature, near the specified value when decreasing air temperature and near the specified value when stationary?

0 V increasing

5 V decreasing

2.5 V stationary

Go to Step 18

Go to Step 23

18

Inspect the air temperature door for a mechanical failure or a condition that allows excessive travel of the door.

Did you find and correct the condition?

--

Go to Step 26

--

19

Test the ignition 3 voltage circuit of the HVAC control module for an open, a high resistance or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 26

Go to Step 20

20

Test the ground circuit of the HVAC control module for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 26

Go to Step 23

21

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 26

Go to Step 22

22

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 26

Go to Step 24

23

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 26

Go to Step 25

24

Important:: Perform the recalibration procedure for the air temperature actuator.

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

Did you complete the replacement?

--

Go to Step 26

--

25

Important:: Perform the recalibration procedure for the HVAC control module.

Replace the HVAC control module. Refer to Heater and Air Conditioning Control Replacement .

Did you complete the replacement?

--

Go to Step 26

--

26

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2