GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2006 🢒 STS 🢒 HVAC 🢒 Heating, Ventilation and Air Conditioning 🢒 Noise Diagnosis - Air Conditioning (A/C) System

Step

Action

Yes

No

DEFINITION: Noise Originating from the A/C compressor, drive belt, or the A/C lines.

1

Were you sent here from HVAC Symptoms or another diagnostic table?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. A/C system noises can be generally categorized into 3 areas:
    2. • Screeching, squealing, or chirping noises
    • Moaning noises
    • Vibration/rattle noises
  2. Start the engine.
  3. Ensure that the front and rear A/C is ON.

Do you hear a screeching, squealing noise when you engage the A/C?

Go to Step 3

Go to Step 9

3

With the engine OFF, inspect the drive belt for excessive wear. Refer to Drive Belt Excessive Wear Diagnosis in 3.6L engine or Drive Belt Falls Off and Excessive Wear Diagnosis in 4.4L engine or Drive Belt Excessive Wear Diagnosis in 4.6L engine.

Is the drive belt excessively worn?

Go to Step 18

Go to Step 4

4

Inspect the drive belt tension. Refer to Drive Belt Tensioner Diagnosis or Drive Belt Tensioner Diagnosis or Drive Belt Tensioner Diagnosis .

Is the drive belt tension correct?

Go to Step 19

Go to Step 5

5

Inspect the drive belt for excessive oil coverage.

Is the drive belt covered with oil?

Go to Step 17

Go to Step 6

6
  1. Start the engine.
  2. Ensure that the front A/C is ON.
  3. Inspect the compressor and the clutch.

Is the compressor locked up?

Go to Step 23

Go to Step 7

7

Is the A/C compressor clutch slipping?

Go to Step 23

Go to Step 8

8

Using a stethoscope, listen to the A/C compressor for any abnormal noises.

Is the compressor causing an abnormal noise?

Go to Step 15

Go to Step 10

9

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

Go to Step 10

Go to Step 12

10

Listen to the A/C compressor components and mounting for noise concerns using a stethoscope.

Are any of these components loose, damaged, or excessively worn?

Go to Step 20

Go to Step 11

11
  1. Start the engine.
  2. Engage the A/C compressor clutch.
  3. Using a stethoscope, move around the entire refrigerant plumbing system, listening for any abnormal noises caused by component ground-out.

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

Go to Step 22

Go to Step 13

12

Does a vibration or rattle noise exist when the A/C clutch is engaged?

Go to Step 13

Go to Step 14

13

Does the noise stop when the A/C clutch is disengaged?

Go to Step 15

Go to Step 14

14
  1. Idle the engine in PARK with the A/C compressor clutch engaged.
  2. Using a stethoscope, move around the entire A/C system listening for any abnormal noises caused by a component.

Do any of the A/C components cause an abnormal noise?

Go to Step 21

Go to Step 24

15

Verify that the A/C system is properly charged. Refer to Refrigerant System Capacities .

Is the A/C system properly charged?

Go to Step 24

Go to Step 16

16

Recharge the A/C system to specification. Refer to Refrigerant Recovery and Recharging .

Is the abnormal compressor noise still present?

Go to Step 24

Go to Step 25

17

Repair the oil leak. Refer to the appropriate repair procedure in Engine Mechanical.

Is the repair complete?

Go to Step 25

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18

Replace the drive belt. Refer to Air Conditioning Compressor and Power Steering Pump Belt Replacement or Water Pump and Air Conditioning Compressor and Power Steering Pump Belt Replacement or Drive Belt Removal and Drive Belt Installation .

Is the replacement complete?

Go to Step 25

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19

Replace the drive belt tensioner. Refer to Air Conditioning Compressor and Power Steering Pump Belt Tensioner Replacement or Drive Belt Tensioner Replacement - Air Conditioning, Power Steering, and Water Pump or Drive Belt Tensioner Removal and Drive Belt Tensioner Installation

Is the replacement complete?

Go to Step 25

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20

Repair or replace the A/C compressor mounting component.

Is the repair complete?

Go to Step 25

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21

Repair or replace the component which is causing the moaning concern as needed.

Is the repair complete?

Go to Step 25

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22

Correctly route or insulate the A/C component.

Is the repair complete?

Go to Step 25

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23

Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement .

Is the replacement complete?

Go to Step 25

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24

The concern may be caused by an engine related component. Refer to Drive Belt Vibration Diagnosis in 3.6L engine or Drive Belt Rumbling and Vibration Diagnosis in 4.4L engine or Drive Belt Vibration Diagnosis in 4.6L engine.

Did you find and correct the condition?

Go to Step 25

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25

Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Step 2