For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you perform the HVAC Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - HVAC Systems - Automatic in HVAC Systems - Automatic
2 |

1. Sit inside the vehicle.
2. Close the vehicle doors and windows.
3. Turn ON the ignition, with the engine OFF.
4. Set the blower speed to high.
5. Set the temperature control to full cold.
6. Set the mode control so the air comes out the IP vents.
7. Set the A/C to OFF.

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. Turn the A/C ON.

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 in HVAC Systems - Automatic

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

• | Screech/Squealing/Chirping 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 11

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.
2. Replace the A/C compressor drive belt. Refer to Drive Belt Replacement in Engine Mechanical.

Did you complete the repair?

Go to Step 25

--

7 | Is the A/C compressor clutch slipping or the compressor locked up? | Go to Step 8 | Go to Step 9
8 |

1. Verify the A/C system is properly charged.
2. Repair or replace the A/C compressor/component as necessary.

Did you complete the repair?

Go to Step 25

--

9 |

1. Start the engine and allow the engine to idle in PARK.
2. Engage the A/C compressor clutch.
3. Using a stethoscope, check the A/C compressor drive belt idler pulley and tensioner for any abnormal noises.

Is the idler pulley and tensioner causing an abnormal noise?

Go to Step 10

Go to Step 11

10 | Replace the A/C compressor drive belt idler pulley or tensioner as necessary. Did you complete the repair? | Go to Step 25 | --
11 | Does a moaning noise exist when the A/C clutch is engaged? | Go to Step 12 | Go to Step 20
12 | Important: A moaning/rumbling noise originating from the compressor could be caused by the system being less than 1/2 pound low on charge. The performance test may not detect the system being under charged less than 1/2 pound. Perform a system performance test to verify the A/C system is properly charged. Refer to Air Conditioning (A/C) System Performance Test .

Is the A/C system properly charged?

Go to Step 14

Go to Step 13

13 |

1. Recover and recharge the A/C system. Refer to Refrigerant Recovery and Recharging .
2. Start the engine and allow the engine to idle in PARK.
3. Engaged the A/C compressor clutch.

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

Go to Step 14

Go to Step 25

14 | 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 15 | Go to Step 16
15 | Repair or replace the A/C compressor mounting, idler pulley or tensioner/tensioner pulley as needed. Did you complete the repair? | Go to Step 25 | --
16 |

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 17

Go to Step 18

17 | Repair or replace the component which is causing the moaning concern as needed. Did you complete the repair? | Go to Step 25 | --
18 | Does the concern go away with the A/C clutch disengaged and the engine idling in PARK? | Go to Step 19 | Go to Vibration Analysis - Engine in Vibration Diagnosis and Correction
19 | Replace the A/C Compressor. Refer to Air Conditioning Compressor Replacement . Did you complete the repair? | Go to Step 25 | --
20 | Does a vibration or rattle noise exist when the A/C clutch is engaged? | Go to Step 21 | System OK
21 | 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 15 | Go to Step 22
22 |

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 23

Go to Step 24

23 | Repair or replace the component which is causing the vibration/rattle concern as needed. Did you complete the repair? | Go to Step 25 | --
24 | Is the vibration/rattle coming from the A/C compressor internally? | Go to Step 19 | Go to Vibration Analysis - Engine in Vibration Diagnosis and Correction
25 | Operate the system in order to verify the repair. Did you find and correct the condition? | System OK | Go to Step 2