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Makes 🢒 Chevrolet 🢒 2001 🢒 Express 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 HVAC Compressor Clutch Does Not Engage

HVAC Compressor Clutch Does Not Engage Except 6.5L

Test Description

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

  1. The A/C compressor relay output is disabled if engine coolant temperature is above 121°C (250°F).

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

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: A/C compressor clutch will not engage when an A/C request has been made and a Powertrain DTC has not been set.

1

Did you perform the Symptoms-HVAC Systems-Manual Check?

Go to Step 2

Go to Symptoms - HVAC Systems - Manual

2

  1. Install a scan tool.
  2. Start the engine.
  3. With a scan tool, observe the ECT parameter in the Powertrain data list.

Does the scan tool indicate that the ECT parameter is below 121°C (250°F)?

Go to Step 3

Go to Engine Overheating in Engine Cooling

3

Important: 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 Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 4

4
  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 for approximately 2 minutes.
  4. Turn OFF the ignition.
  5. Install the J 43600 ACR 2000.
  6. Record the ambient temperature at the vehicle.
  7. Record readings of the low and high side STATIC pressures.
  8. Compare the pressure values with the specifications for the ambient air temperature. Refer to Air Conditioning (A/C) System Performance Test in Heating, Ventilation and Air Conditioning.

Are the pressure values within the specifications for the ambient air temperature, and within 103 kPa (15 psi) of each other?

Go to Step 5

Go to Leak Testing in Heating, Ventilation and Air Conditioning

5

Is the HVAC control assembly inoperative?

Go to Step 7

Go to Step 6

6
  1. Start the engine.
  2. With a scan tool, observe the A/C Request Signal parameter in the Engine Data 2 data list.
  3. Place the A/C request switch in the ON position.

Does the scan tool indicate that the A/C Request parameter is YES?

Go to Step 9

Go to Step 10

7

Test the voltage supply circuits to the HVAC control assembly 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 8

8

Test the ground circuit to the HVAC control assembly for an 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

9

Does the scan tool indicate the A/C Compressor Cycling Switch parameter is closed?

Go to Step 16

Go to Step 11

10
  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 YES?

Go to Step 32

Go to Step 12

11
  1. Turn OFF the ignition.
  2. Disconnect the A/C low pressure cutout switch.
  3. Connect a 3 amp fused jumper wire between the A/C low pressure cutout switch signal and ground circuits.
  4. Start the engine.
  5. With a scan tool, observe the A/C Compressor Cycling Switch parameter.

Does the scan tool indicate the A/C Compressor Cycling Switch parameter is closed?

Go to Step 29

Go to Step 14

12
  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 13

13

Measure the voltage from the A/C request signal circuit at the PCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Does the voltage measure near Battery Voltage?

Go to Step 33

Go to Step 31

14

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 15

15

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 33

16

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 17

Go to Step 19

17
  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 18

Go to Step 27

18
  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 28

Go to Step 22

19
  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 20

Go to Step 26

20
  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 28

Go to Step 21

21

Does the test lamp remain illuminated with each command?

Go to Step 24

Go to Step 25

22

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 23

23

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 30

24

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 33

25

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 33

26

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

--

27

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

--

28

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 34

29

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 35

30

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 37

31

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 38

32

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 36

33

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

34

Replace the A/C compressor clutch relay. Refer to Compressor Relay Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

Go to Step 40

--

35

Replace the A/C low pressure switch. Refer to Air Conditioning (A/C) Low Pressure Switch Replacement in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

Go to Step 40

--

36

Replace the A/C high pressure switch. Refer to Air Conditioning (A/C) High Pressure Switch Replacement in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

Go to Step 40

--

37

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

Did you complete the replacement?

Go to Step 40

--

38

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

Did you complete the replacement?

Go to Step 40

--

39

Important:  Perform the programming procedure for the PCM.

Replace the PCM. Refer to one of the following procedures:

    •  Powertrain Control Module Replacement in Engine Controls - 4.3L
    •  Powertrain Control Module Replacement in Engine Controls - 5.0L, 5.7L
    •  Powertrain Control Module Replacement in Engine Controls - 8.1L

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 4

HVAC Compressor Clutch Does Not Engage 6.5L (L65)

Test Description

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

  1. The A/C compressor relay output is disabled if engine coolant temperature is above 121°C (250°F).

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

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: A/C compressor clutch will not engage when an A/C request has been made and a Powertrain DTC has not been set.

1

Did you perform the Symptoms-HVAC Systems-Manual Check?

Go to Step 2

Go to Symptoms - HVAC Systems - Manual

2

  1. Install a scan tool.
  2. Start the engine.
  3. With a scan tool, observe the ECT parameter in the Powertrain data list.

Does the scan tool indicate that the ECT parameter is below 121°C (250°F)?

Go to Step 3

Go to Engine Overheating in Engine Cooling

3

Important: 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 Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 4

4
  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, then allow the A/C system to equalize for approximately 2 minutes.
  4. Turn OFF the ignition.
  5. Install the J 43600 ACR 2000.
  6. Record the ambient temperature at the vehicle.
  7. Compare the pressure values with the specifications for the ambient air temperature.

Are the pressure values within the specifications for the ambient air temperature, and within 103 kPa (15 psi) of each other?

Go to Step 5

Go to Leak Testing in Heating, Ventilation and Air Conditioning

5

Is the HVAC control assembly inoperative?

Go to Step 7

Go to Step 6

6
  1. Start the engine.
  2. With a scan tool, observe the A/C Request parameter in Engine Data 1 data list.
  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 13

Go to Step 9

7

Test the voltage supply circuits to the HVAC control assembly 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 37

Go to Step 8

8

Test the ground circuit to the HVAC control assembly for an 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 37

Go to Step 28

9
  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 29

Go to Step 10

10
  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 request circuits at the A/C low 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 26

Go to Step 11

11
  1. Turn OFF the ignition.
  2. Reconnect the A/C high pressure switch.
  3. Reconnect the A/C low pressure switch.
  4. 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 37

Go to Step 12

12

Measure the voltage from the A/C Request signal circuit at the PCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Does the voltage measure near Battery Voltage?

Go to Step 30

Go to Step 28

13

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 14

Go to Step 16

14
  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 15

Go to Step 24

15
  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 25

Go to Step 19

16
  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 17

Go to Step 23

17
  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 25

Go to Step 18

18

Does the test lamp remain illuminated with each command?

Go to Step 21

Go to Step 22

19

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 37

Go to Step 20

20

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 37

Go to Step 27

21

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 37

Go to Step 30

22

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 37

Go to Step 30

23

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 37

--

24

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 37

--

25

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 37

Go to Step 31

26

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 37

Go to Step 32

27

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 37

Go to Step 34

28

Inspect for poor connections at the harness connector of the 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 37

Go to Step 35

29

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 37

Go to Step 33

30

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 37

Go to Step 36

31

Replace the A/C compressor clutch relay. Refer to Compressor Relay Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

Go to Step 37

--

32

Replace the A/C low pressure switch. Refer to Air Conditioning (A/C) Low Pressure Switch Replacement in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

Go to Step 37

--

33

Replace the A/C high pressure switch. Refer to Air Conditioning (A/C) High Pressure Switch Replacement in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

Go to Step 37

--

34

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

Did you complete the replacement?

Go to Step 37

--

35

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

Did you complete the replacement?

Go to Step 37

--

36

Important:  Perform the programming procedure for the PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 6.5L.

Did you complete the replacement?

Go to Step 37

--

37

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 4