For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Were you sent here from the HVAC System Check? | -- | Go to Step 2 | Go to HVAC System Check
2 |

1. Sit inside the vehicle.
2. Close the vehicle doors and windows.
3. Turn the ignition switch to the ON position; engine OFF.
4. Turn the blower switch to position 5 (high).
5. Set the temperature control to the full cold position.
6. Set the mode control to the UPPER (I/P outlets).
7. Depress the A/C button to the OFF position.

Is an abnormal noise present?

--

Go to Noise Diagnosis - Blower Motor

Go to Step 3

3 |

1. Start the engine and allow the engine to idle in PARK.
2. Depress the A/C button to the ON position.

Is the A/C clutch engaged and supplying cold air to the passenger compartment?

--

Go to Step 4

Go to HVAC Compressor Clutch Does Not Engage

4 | A/C system noises can be generally categorized into three areas:

• | Screech/Squealing noises

• | Moaning noises

• | Vibration/Rattle noises

Is a screech/squealing noise heard when the A/C clutch is engaged?

--

Go to Step 5

Go to Step 12

5 | Inspect the A/C compressor drive belt for excessive wear or oil coverage. Is the drive belt excessively worn or covered with oil? | -- | Go to Step 6 | Go to Step 7
6 |

1. Repair the source of the oil leak, if a leak was present.

Refer to Oil Leak Diagnosis in Engine Mechanical.

2. Replace the A/C compressor drive belt.

Refer to Drive Belt Replacement in Engine Mechanical.

Is the repair complete?

--

Go to Step 28

--

7 |

1. A/C compressor clutch engaged and engine idling in PARK.
2. Using a stethoscope, check the A/C compressor drive belt tensioner pulley for any abnormal noises.
3. Turn the ignition switch to the OFF position.
4. Check the tensioner for proper spring load

Is the tensioner pulley operating normally with proper tension and without noise?

--

Go to Step 9

Go to Step 8

8 | Replace the A/C compressor drive belt tensioner/tensioner pulley as needed. Refer to Drive Belt Tensioner Replacement in Engine Mechanical. Is the repair complete? | -- | Go to Step 28 | --
9 | Is the A/C compressor locked up? | -- | Go to Step 10 | Go to Step 11
10 |

1. Recover the refrigerant.
2. Replace the A/C compressor.

Refer to Air Conditioning Compressor Replacement .

Is the repair complete?

--

Go to Step 29

--

11 |

1. Recover the refrigerant.
2. Replace the A/C compressor clutch coil assembly.

Refer to Air Conditioning Clutch Coil Replacement .

Is the repair complete?

--

Go to Step 29

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12 | Does a moaning noise exist when the A/C clutch is engaged? | -- | Go to Step 13 | Go to Step 21
13 |

1. Connect an R-134a manifold gage set to the low and high side service ports on the vehicle refrigerant system.
2. Increase and maintain the engine speed at 2000 RPM, in PARK.
3. Engage the A/C clutch.
4. Check the low and high side refrigerant pressures.
5. Compare the pressure readings to those listed in the System Performance Chart.

Refer to System Performance Test .

Are the high and low side refrigerant pressures within the normal specified limits?

--

Go to Step 15

Go to Step 14

14 |

1. Recover the refrigerant, evacuate and charge the refrigerant system to specifications.
2. Start the engine and allow the engine to idle in PARK.
3. Engage the A/C compressor clutch.

Does the moaning noise exist when the A/C clutch is engaged?

--

Go to Step 30

Go to Step 15

15 | Inspect the A/C compressor mounting, idler pulley, and tensioner for concerns using a stethoscope. Are any of these components loose, damaged or excessively worn? | -- | Go to Step 16 | Go to Step 17
16 | Repair or replace the A/C compressor mounting or tensioner/tensioner pulley as needed. Refer to Drive Belt Tensioner Replacement in Engine Mechanical. Is the repair or replacement complete? | -- | Go to Step 28 | --
17 |

1. A/C compressor clutch engaged and engine idling in PARK.
2. Using a stethoscope, move around the entire refrigerant plumbing system checking for any abnormal noises being caused by component ground-out.

Are any of the A/C components grounding out and causing a noise?

--

Go to Step 18

Go to Step 19

18 |

1. Recover the refrigerant, if necessary.
2. Repair or replace the component which is causing the moaning concern as needed.

Is the repair or replacement complete?

--

Go to Step 29

--

19 | Does the concern go away with the A/C clutch disengaged and the engine idling in PARK? | -- | Go to Step 20 | Go to Engine Related Vibration in Vibration Diagnosis and Correction
20 |

1. Recover the refrigerant.
2. Replace the A/C compressor.

Refer to Air Conditioning Compressor Replacement .

Is the repair complete?

--

Go to Step 29

--

21 | Does a vibration or rattle noise exist when the A/C clutch is engaged? | -- | Go to Step 22 | System OK
22 | Inspect the A/C compressor mounting, idler pulley, and tensioner for concerns using a stethoscope. Are any of these components loose, damaged or excessively worn? | -- | Go to Step 16 | Go to Step 23
23 | Is the A/C compressor drive belt misaligned ? | -- | Go to Step 24 | Go to Step 25
24 | Repair any alignment concern with the A/C pulley system and replace the drive belt as needed. Refer to Drive Belt Replacement in Engine Mechanical. Is the repair complete? | -- | Go to Step 28 | --
25 |

1. A/C compressor clutch engaged and engine idling in PARK.
2. Using a stethoscope, move around the entire A/C system checking for any abnormal noises being caused by a component.

Are any of the A/C components causing an abnormal noise?

--

Go to Step 26

Go to Step 27

26 |

1. Recover the refrigerant.
2. Repair or replace the component which is causing the vibration/rattle concern as needed.

Is the repair complete?

--

Go to Step 29

--

27 | Is the vibration/rattle coming from the A/C compressor internally? | -- | Go to Step 10 | Go to Engine Related Vibration in Vibration Diagnosis and Correction
28 |

1. Turn OFF the ignition switch.
2. Reconnect or install any connectors or components which were disconnected or removed.
3. Recheck for the presense of the A/C system noise.

Is the A/C system noise still present?

--

Go to Step 2

Go to HVAC System Check

29 |

1. Evacuate and charge the refrigerant system.
2. Leak test the refrigerant system.

Refer to Leak Testing .

Are the actions completed?

--

Go to Step 30

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30 | Recheck for the presense of the A/C system noise. Is the A/C system noise still present? | -- | Go to Step 2 | Go to HVAC System Check