GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Corvette 🢒 Body and Accessories 🢒 Data Link Communications 🢒 HVAC Compressor Clutch Does Not Engage

A/C Compressor Clutch Does Not Engage <<CJ2>>

Step

Action

Value(s)

Yes

No

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

1

Were you sent here from the HVAC System Check (CJ2)?

--

Go to Step 2

Go to HVAC System Check

2
  1. Turn the ignition switch to the OFF position.
  2. Install both the high and low A/C refrigerant pressure gages.
  3. Read the refrigerant pressure with the engine off.
    4. • Refrigerant pressure in the high and low sides should equal each other after the A/C system has come to rest.
    • Refrigerant pressure will fluctuate depending on ambient temperature.
    • Proper clutch operation depends on correct refrigerant charge, low freon charge will shut off A/C compressor operation.

Is the high and low side refrigerant pressures below the specified value?

345 kPa (50 psi)

Go toLeak Testing

Go to Step 3

3

Is the high and low side refrigerant pressures above the specified value?

690 kPa (100 psi)

Go to Step 4

Go to Step 5

4

Evacuate and recharge the A/C system according to proper refrigerant fill specifications.

Has the A/C system been recharged properly?

--

Go to HVAC System Check

--

5

Inspect the A/C MiniFuse ® #24 for an open circuit.

Is the fuse open?

--

Go to Step 6

Go to Step 27

6
  1. Remove the A/C CLU Micro Relay #34.
  2. Disconnect the A/C compressor clutch connector.
  3. Using a DMM, measure for continuity between terminal A of the A/C compressor clutch connector and ground.

Is CKT 59 continuous to ground?

--

Go to Step 7

Go to Step 8

7

Locate and repair a short to ground in CKT 59 between the underhood electrical center and the A/C compressor clutch connector.

Is the repair complete?

--

Go to HVAC System Check

--

8
  1. A/C CLU Micro Relay #34 still removed.
  2. A/C compressor clutch connector still disconnected.
  3. Connect a fused jumper between the IGN feed for the switch side of the A/C CLU Micro Relay #34 and the terminal used to feed CKT 59 in the underhood electrical center.
  4. Using a DMM, measure the voltage at the A/C compressor clutch connector terminal A.

Is the voltage within the specified values?

10.0-14.0V

Go to Step 10

Go to Step 9

9

Locate and repair an open or a high resistance in CKT 59.

Is the repair complete?

--

Go to HVAC System Check

--

10

Using a DMM, measure for continuity between terminal B of the A/C compressor clutch connector and ground.

Is the resistance to ground less than the specified value?

0.5ohms

Go to Step 12

Go to Step 11

11

Locate and repair an open or a high resistance in CKT 150.

Is the repair complete?

--

Go to HVAC System Check

--

12
  1. Disconnect the powertrain control module (PCM) connector C1.
  2. Reinstall the A/C CLU Micro Relay #34.
  3. Connect a fused jumper between the PCM connector C1 terminal 39 and ground.
  4. Turn the ignition switch to the ON position.
  5. Using a DMM, measure the voltage at the A/C compressor clutch connector terminal A.

Is the voltage within the specified values?

10.0-14.0V

Go to Step 13

Go to Step 14

13
  1. Remove the fused jumper from the PCM connector C1 terminal 39 and ground.
  2. Reconnect the A/C compressor clutch connector.
  3. Reinstall the fused jumper between the PCM connector C1 terminal 39 and ground.
  4. Turn the ignition switch to the ON position.

Does the A/C compressor clutch engage?

--

Go to Cooling Insufficient - Air Conditioning (A/C) System

Go to Step 26

14
  1. Turn the ignition switch to the OFF position.
  2. Remove the A/C CLU Micro Relay #34.
  3. Using a DMM, measure for continuity between the PCM connector C1 terminal 39 and CKT 459 terminal of the underhood electrical center which is used for the A/C CLU Micro Relay #34.

Is CKT 459 continuous between these two terminals?

--

Go to Step 16

Go to Step 15

15

Locate and repair an open or a high resistance in CKT 459.

Is the repair complete?

--

Go to HVAC System Check

--

16

Replace the A/C CLU Mini Relay #34 and retest the A/C system.

Does replacing the A/C CLU Mini Relay #34 correct the concern?

--

Go to HVAC System Check

Go to Step 17

17
  1. Disconnect the HVAC Control Assembly connector C2.
  2. Connect a DMM between the PCM connector C2 terminal 58 and the HVAC Control Assembly connector terminal D12.
  3. Measure CKT 1049 and CKT 1038 (see wiring diagram) for continuity between these two connectors.

Is CKT 1049 and CKT 1038 continuous between these two connectors?

--

Go to Step 19

Go to Step 18

18

Locate and repair an open or a high resistance in CKT 1049 or CKT 1038.

Is the repair complete?

--

Go to HVAC System Check

--

19
  1. Disconnect the Star Connector 1 bus bar.
  2. Connect a DMM between the PCM connector C2 terminal 58 and ground.
  3. Measure CKT 1049 for continuity to ground.

Is CKT 1049 continuous to ground?

--

Go to Step 20

Go to Step 21

20

Locate and repair a short to ground in CKT 1049.

Is the repair complete?

--

Go to HVAC System Check

--

21
  1. Connect a DMM between the HVAC Control Assembly connector terminal D12 and ground.
  2. Measure CKT 1038 for continuity to ground.

Is CKT 1038 continuous to ground?

--

Go to Step 22

Go to Step 23

22

Locate and repair a short to ground in CKT 1038.

Is the repair complete?

--

Go to HVAC System Check

--

23
  1. Disconnect the DMM.
  2. Reconnect all connectors back to their respective modules.
  3. Install the scan tool to the diagnostic link connector.
  4. Start the engine and allow it to idle in Park.
  5. Select the area of the scan tool which will read HVAC button output status.
  6. Depress the A/C button on/off several times.

Does the scan tool read the A/C request being sent by the HVAC Control Assembly?

--

Go to Step 24

Go to Step 25

24

Replace the PCM. Refer to Powertrain Control Module/Throttle Actuator Control Module Replacement .

Is the repair complete?

--

Go to HVAC System Check

--

25

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

Is the repair complete?

--

Go to HVAC System Check

--

26

Replace the A/C compressor clutch. Refer to Compressor Clutch Coil Removal (V7 - Direct Mount) .

Is the repair complete?

--

Go to HVAC System Check

--

27

With the A/C MiniFuse ® #24 installed, check for voltage on both sides of the fuse with a DMM.

Is the voltage within the specified values?

10.0-14.0V

Go to Step 8

Go to Step 28

28

Does the car start and run normally?

--

Go to Step 29

Powertrain On Board Diagnostic (OBD) System Check

29

Replace the underhood electrical center.

Is the repair complete?

--

Go to HVAC System Check

--