GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 GMC K Sierra - 4WD 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 HVAC Compressor Clutch Does Not Engage

Test Description

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

  1. The HVAC control module is inoperative when the module does not respond to any operator control requests.

    2.

  2. When the blower motor is in the OFF position, a voltage is applied to the OFF blower motor control circuit. The A/C system will not operate if a voltage is applied to the OFF blower motor control circuit.

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Compressor Control Schematics

DEFINITION: A/C compressor clutch will not engage when an A/C request has been made and no Powertrain DTC has been set.

Important: 

   • Compressor clutch engagement cannot be used to determine the status of the low pressure switch. The low pressure switch is one of several inputs to the HVAC control module for A/C request authorization. A/C request is one of several inputs to the powertrain control module (PCM) that control A/C compressor clutch engagement.
   • To accurately determine what pressure the A/C low pressure switch opens and closes at use Kent Moore GE-47742 which will allow the technician to measure the switch point pressure at the switch.
   • Using a scan tool, monitor the "low pressure switch" status while monitoring the "low side" pressure at the switch to determine the switch points of the low pressure switch.
   • The low pressure switch "connector seal" must be removed before plugging it into the switch for testing. The "plunger effect" of plugging the connector with seal into the switch induces a pressure on the back side of the switch, this pressure will skew the opening/closing characteristics of the switch 5-10 psi until the pressure bleeds off. The time required for the connection induced pressure to bleed off can take 20 minutes or longer.

1

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

--

Go to Step 2

Go to Symptoms

2

Important: : For A/C compressor operation, outside 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 switch in the ON position.
  4. Place the air temperature control switch in the coldest position.

Does the A/C compressor operate?

--

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

Go to Step 3

3
  1. Park the vehicle inside or in the shade.
  2. Open the windows in order to ventilate the interior of the vehicle.
  3. If the A/C system was operating, allow the A/C system to equalize (about 2 minutes).
  4. Ensure that the ignition key is in the OFF position.
  5. Install the J 39500-B ACR 2000.
  6. Record the ambient temperature at the vehicle.
  7. Record readings of the low and high side STATIC pressures.

Are both the low and high side pressures within 103 kPa (15 psi) of the ambient temperature?

--

Go to Step 4

Go to Leak Testing in Heating, Ventilation and Air Conditioning

4

Is the HVAC control module inoperative?

--

Go to Step 22

Go to Step 5

5
  1. Start the engine.
  2. With a scan tool, observe the A/C request parameter.
  3. Place the A/C request switch in the ON position.

Does the scan tool indicate that the A/C request parameter is ON?

--

Go to Step 8

Go to Step 6

6

Does the A/C request indicator illuminate?

--

Go to Step 7

Go to Step 24

7

IMPORTANT:: Ensure that the blower motor switch is not in the OFF position during this step.

  1. Turn OFF the ignition.
  2. Disconnect the A/C high pressure switch.
  3. Connect a 3 amp fused jumper wire between the A/C request circuits at the A/C high pressure switch connector.
  4. Start the engine.
  5. With a scan tool, observe the A/C request parameter.
  6. Place the A/C request switch in the ON position.

Does the scan tool indicate that the A/C request parameter is ON?

--

Go to Step 34

Go to Step 29

8

Does the scan tool indicate the A/C low pressure switch parameter is closed?

--

Go to Step 10

Go to Step 9

9
  1. Turn OFF the ignition.
  2. Disconnect the A/C low pressure switch.
  3. Connect a 3 amp fused jumper wire between the A/C low pressure switch signal and ground circuits.
  4. Start the engine.
  5. With a scan tool, observe the A/C low pressure switch parameter.

Does the scan tool indicate the A/C low pressure switch parameter is closed?

--

Go to Step 30

Go to Step 25

10

With a scan tool, command the A/C compressor clutch relay ON and OFF.

Does the A/C compressor clutch relay turn ON and OFF with each command?

--

Go to Step 19

Go to Step 11

11
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the coil side voltage supply circuit of the A/C compressor clutch relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 12

Go to Step 18

12
  1. Connect a test lamp between the control circuit of the A/C compressor clutch relay and the coil side voltage supply circuit of the A/C compressor clutch relay.
  2. With a scan tool, command the A/C compressor clutch relay ON and OFF.

Does the test lamp turn ON and OFF with each command?

--

Go to Step 16

Go to Step 13

13

Does the test lamp remain illuminated with each command?

--

Go to Step 15

Go to Step 14

14

Test the control circuit of the A/C compressor clutch relay for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 40

Go to Step 38

15

Test the control circuit of the A/C compressor clutch relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 40

Go to Step 38

16

Inspect for poor connections at the A/C compressor clutch relay. 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 40

Go to Step 17

17

Replace the A/C compressor clutch relay.

Did you complete the replacement?

--

Go to Step 40

--

18

Repair the coil side voltage supply circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 40

--

19
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Probe the switch side voltage supply circuit of the A/C compressor clutch relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 20

Go to Step 21

20
  1. Connect a 10 amp fused jumper wire between the switch side voltage circuit of the A/C compressor clutch relay and the A/C compressor clutch supply voltage circuit of the A/C compressor clutch.
  2. Turn ON the ignition, with the engine OFF.

Does the A/C compressor clutch engage?

--

Go to Step 16

Go to Step 27

21

Repair the switch side voltage supply circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 40

--

22

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

Did you find and correct the condition?

--

Go to Step 40

Go to Step 23

23

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 40

Go to Step 32

24

IMPORTANT:: Ensure that the blower motor switch is not in the OFF position during this step.

Test the OFF blower motor control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 40

Go to Step 32

25

Test the A/C low pressure switch signal circuit for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 40

Go to Step 26

26

Test the ground circuit of the A/C low pressure switch for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 40

Go to Step 38

27

Test the A/C compressor clutch supply voltage circuit at the A/C compressor clutch for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 40

Go to Step 28

28

Test the ground circuit of the A/C compressor clutch for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 40

Go to Step 31

29
  1. Turn OFF the ignition.
  2. Reconnect the A/C high pressure switch.
  3. Test the A/C request signal circuit for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 40

Go to Step 38

30

Inspect for poor connections at the harness connector of the A/C low pressure switch. 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 40

Go to Step 33

31

Inspect for poor connections at the harness connector of the A/C compressor clutch. 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 40

Go to Step 36

32

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 40

Go to Step 37

33

Replace the A/C low pressure switch.

Did you complete the replacement?

--

Go to Step 40

--

34

Inspect for poor connections at the harness connector of the A/C high pressure switch. 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 40

Go to Step 35

35

Replace the A/C high pressure switch.

Did you complete the replacement?

--

Go to Step 40

--

36

Replace the A/C compressor clutch coil. Refer to Air Conditioning Clutch Coil Removal and Air Conditioning Clutch Coil Installation in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

--

Go to Step 40

--

37

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

Did you complete the replacement?

--

Go to Step 40

--

38

Inspect for poor connections at the harness connector of the powertrain control module (PCM). 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 40

Go to Step 39

39

Important::  Perform the reprogramming procedure for the PCM.

Replace the Vehicle Control Module (VCM) or Powertrain Control Module (PCM). Refer to VCM Replacement/Programming in Engine Controls - 4.3L or Powertrain Control Module Replacement in Engine Controls - 4.8L, 5.3L, and 6.0L.

Did you complete the replacement?

--

Go to Step 40

--

40

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3