For 1990-2009 cars

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? | -- | 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 freon pressure gages.
3. Read the freon pressure with the engine off.

• | Freon pressure in the high and low sides should equal each other after the A/C system has come to rest.

• | Freon 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 freon pressures below the specified value?

345 kPa (50 psi)

Go to Leak Testing

Go to Step 3

3 | Is the high and low side freon 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 freon fill specifications. Has the A/C system been recharged properly? | -- | Go to HVAC System Check | --
5 | Check the A/C CLU Fuse for an open circuit. Is the fuse open? | -- | Go to Step 6 | Go to Step 7
6 | 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 | --
7 |

1. Remove the A/C CLU Micro Relay #13 from the underhood electrical center.
2. Disconnect the A/C compressor clutch connector.
3. Connect a fused jumper between the ignition feed terminal for the switch side of the A/C CLU Micro Relay #13 and the terminal (F8) used to feed CKT 59 in the underhood electrical center.
4. Connect a J 39200 between the A/C compressor clutch connector terminal B and ground.
5. Turn the ignition switch to the ON position.
6. Measure the available voltage at the A/C compressor clutch connector terminal B.

Is the voltage within the specified values?

B+

Go to Step 9

Go to Step 8

8 | Locate and repair an open or a high resistance in CKT 59. Is the repair complete? | -- | Go to HVAC System Check | --
9 | Using a J 39200 , 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? | 0-2 ohms | Go to Step 11 | Go to Step 10
10 | Locate and repair an open or a high resistance in CKT 1050. Is the repair complete? | -- | Go to HVAC System Check | --
11 |

1. Disconnect the powertrain control module (PCM) connector C2.
2. Reinstall the A/C CLU Micro Relay #13.
3. Connect a fused jumper between the PCM connector C2 terminal 39 and ground.
4. Turn the ignition switch to the ON position.
5. Using a J 39200 , measure the voltage between the A/C compressor clutch connector terminal B and ground.

Is the voltage within the specified values?

B+

Go to Step 12

Go to Step 13

12 |

1. Remove the fused jumper from the PCM connector C2 terminal 39 and ground.
2. Reconnect the A/C compressor clutch connector.
3. Reinstall the fused jumper between the PCM connector C2 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 23

13 |

1. Turn the ignition switch to the OFF position.
2. Remove the A/C CLU Micro Relay #13.
3. Using a J 39200 , measure for continuity between the PCM connector C2 terminal 39 and the CKT 459 terminal (F7) of the underhood electrical center which is used for the A/C CLU Micro Relay #13.

Is CKT 459 continuous between these two terminals?

0-2 ohms

Go to Step 15

Go to Step 14

14 | Locate and repair an open or a high resistance in CKT 459. Is the repair complete? | -- | Go to HVAC System Check | --
15 | Replace the A/C CLU Mini Relay #13 and retest the A/C system. Does replacing the A/C CLU Mini Relay #13 correct the concern? | -- | Go to HVAC System Check | Go to Step 16
16 |

1. Disconnect the HVAC control head connector C2.
2. Connect a J 39200 between the PCM connector C2 terminal 22 and the HVAC control head connector C2 terminal B.
3. Measure CKT 762 for resistance between these two connectors.

Is CKT 762 resistance between the specified values?

0-2 ohms

Go to Step 18

Go to Step 17

17 | Locate and repair an open or a high resistance in CKT 762. Is the repair complete? | -- | Go to HVAC System Check | --
18 |

1. Connect a J 39200 between the PCM connector C2 terminal 22 and ground.
2. Measure CKT 762 for continuity to ground.

Is CKT 762 continuous to ground?

--

Go to Step 19

Go to Step 20

19 | Locate and repair a short to ground in CKT 762. Is the repair complete? | -- | Go to HVAC System Check | --
20 |

1. Disconnect the J 39200 .
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 head?

--

Go to Step 21

Go to Step 22

21 |

1. Check connection between the PCM and the underhood accessory wiring junction block.
2. If OK, replace the PCM. Refer to Powertrain Control Module Replacement/Programming in Engine Controls.

Is the repair complete?

--

Go to HVAC System Check

--

22 | Replace the HVAC control head. Refer to Control Assembly Replacement . Is the repair complete? | -- | Go to HVAC System Check | --
23 | Replace the A/C compressor clutch. Refer to Compressor Clutch Plate/Hub Assembly Replacement . Is the repair complete? | -- | Go to HVAC System Check | --