GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 Eldorado 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 HVAC Compressor Clutch Does Not Engage

Test Description

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

  1. The A/C compressor relay output is disabled if engine coolant temperature is above 125°C (257°F).

  1. Activate the A/C system by placing the mode switch in any position except OFF, and by placing the air temperature control switch in a cold setting, When operating the A/C system, use bi-level mode for consistent testing.

    2.

  2. An inoperative HVAC control module does not respond to operator control requests to enable the A/C compressor. The blower motor may still operate independent of the A/C controls.

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: The 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 HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2

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

Does the scan tool indicate that the ECT parameter is above 125°C (257°F)?

Go to Engine Overheating in Engine Cooling

Go to Step 3

3

Important: The 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 not in direct sunlight.
  2. Open the window in order to ventilate the interior of the vehicle.
  3. If the A/C system was operating, then wait for approximately 2 minutes.
  4. Turn OFF the ignition.
  5. Install J 43600 .
  6. Record the ambient air temperature at the vehicle.
  7. Record readings of the low and high side STATIC pressures.
  8. Compare the low and high side pressure values with the allowable limits for the recorded ambient air temperature. Refer to Air Conditioning (A/C) System Performance Test in Heating, Ventilation and Air Conditioning.

Are the pressure values within 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 module inoperative?

Go to Step 7

Go to Step 6

6
  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, observe the A/C OFF Switch parameter in the Climate Control Panel (CCP) under Inputs.
  3. Cycle the A/C switch ON and OFF.

Does the scan tool parameter turn ON and OFF each time the switch is pressed?

Go to Step 9

Go to Step 32

7

Test the battery positive voltage circuit to 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 43

Go to Step 8

8

Test the ground circuit of the HVAC control module 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 43

Go to Step 32

9
  1. If the A/C system was operating, then wait for approximately 2 minutes.
  2. With a scan tool, observe the Hi and Low Refrig. Pressure Sw. in Heating and Air Conditioning under Inputs.

Does the scan tool indicate that both the Hi and Low Refrig. Pressure Sw. are Closed?

Go to Step 13

Go to Step 10

10

Is the Hi Refrig. Pressure Sw. Open?

Go to Step 11

Go to Step 12

11
  1. Turn OFF the ignition.
  2. Disconnect the A/C high pressure switch.
  3. Connect a 3-amp fused jumper across the A/C high pressure switch connector.
  4. Start the engine.
  5. With a scan tool, observe the Hi Refrig. Pressure Sw. parameter.

Is the Hi Refrig. Pressure Sw. parameter closed?

Go to Step 34

Go to Step 15

12
  1. Turn OFF the ignition.
  2. Disconnect the A/C low pressure switch.
  3. Connect a 3-amp fused jumper across the A/C low pressure switch connector.
  4. Start the engine.
  5. With a scan tool, observe the Low Refrig. Pressure Sw. parameter.

Is the Low Refrig. Pressure Sw. parameter closed?

Go to Step 30

Go to Step 16

13
  1. Start the engine.
  2. With a scan tool, observe the A/C Possible parameter in Heating and Air Conditioning under Inputs.
  3. Place the A/C system in the ON position.

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

Go to Step 14

Go to Step 33

14
  1. With a scan tool, observe the A/C Relay Commanded parameter in the Powertrain data list.
  2. Place the air temperature switch in the coldest position.
  3. Place the A/C system in the ON position.

Does the scan tool indicate that the A/C Relay Commanded parameter is On?

Go to Step 17

Go to Step 35

15
  1. Turn OFF the ignition.
  2. Reconnect the A/C high pressure switch.
  3. Test the input circuit of the A/C high pressure switch 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 43

Go to Step 35

16
  1. Turn OFF the ignition.
  2. Connect the A/C low pressure switch.
  3. Test the input circuit of the A/C low pressure switch 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 43

Go to Step 35

17

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

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

Go to Step 18

Go to Step 20

18
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Probe the battery positive voltage circuit of the A/C compressor clutch relay switch side with a test lamp.

Does the test lamp illuminate?

Go to Step 19

Go to Step 28

19

Connect a 10-amp fused jumper between the switch side voltage circuit and the supply voltage circuit of the A/C compressor clutch.

Does the A/C compressor clutch engage?

Go to Step 29

Go to Step 23

20
  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 of the supply voltage circuit of the A/C compressor clutch relay with a test lamp.

Does the test lamp illuminate?

Go to Step 21

Go to Step 27

21
  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 29

Go to Step 22

22

Does the test lamp remain illuminated with each command?

Go to Step 25

Go to Step 26

23

Test the 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 43

Go to Step 24

24

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 43

Go to Step 31

25

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 43

Go to Step 35

26

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

Did you find and correct the condition?

Go to Step 43

Go to Step 35

27

Repair the coil side of the 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 43

--

28

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

Did you complete the repair?

Go to Step 43

--

29

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 43

Go to Step 36

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 43

Go to Step 37

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 43

Go to Step 40

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 43

Go to Step 41

33

Inspect for poor connections at the 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 43

Go to Step 39

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 43

Go to Step 38

35

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 43

Go to Step 42

36

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 43

--

37

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 43

--

38

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 43

--

39

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

Did you complete the replacement?

Go to Step 43

--

40

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

Did you complete the replacement?

Go to Step 43

--

41

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

Did you complete the replacement?

Go to Step 43

--

42

Important: Program the PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 4.6L.

Did you complete the replacement?

Go to Step 43

--

43

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 4