GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2000 🢒 Montana 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Noise Diagnosis - Air Conditioning (A/C) System

Step

Action

Value(s)

Yes

No

1

Were you sent here from the HVAC System Check?

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Go to Step 2

Go to Control Assembly Description in HVAC System -- Manual

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?

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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?

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Go to Step 4

Go to HVAC Compressor Clutch Does Not Engage in HVAC System -- Manual

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?

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Go to Step 5

Go to Step 14

5

Inspect the A/C compressor drive belt for excessive wear or oil coverage.

Is the drive belt excessively worn or covered with oil?

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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?

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Go to Step 30

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7
  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 for any abnormal noises.

Is the idler pulley operating normally without abnormal noise?

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Go to Step 9

Go to Step 8

8

Replace the A/C compressor drive belt idler pulley. Refer to Drive Belt Idler Pulley Replacement in Engine Mechanical.

Is the repair complete?

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Go to Step 30

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9
  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?

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Go to Step 11

Go to Step 10

10

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?

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Go to Step 30

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11

Is the A/C compressor locked up?

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Go to Step 12

Go to Step 13

12
  1. Recover the refrigerant.
  2. Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement .

Is the repair complete?

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Go to Step 31

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13
  1. Recover the refrigerant.
  2. Replace the A/C compressor clutch coil assembly. Refer to Air Conditioning Clutch Coil Replacement .

Is the repair complete?

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Go to Step 31

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14

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

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Go to Step 15

Go to Step 23

15
  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.

    6. Refer to Cooling Insufficient - Air Conditioning (A/C) System .

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

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Go to Step 17

Go to Step 16

16
  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. Engaged the A/C compressor clutch.

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

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Go to Step 32

Go to Step 17

17

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?

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Go to Step 18

Go to Step 19

18

Repair or replace the A/C compressor mounting, idler pulley or tensioner/tensioner pulley as needed.

    • For A/C compressor drive belt idler pulley replacement, refer to Drive Belt Idler Pulley Replacement in Engine Mechanical.
    • For A/C compressor drive belt tensioner/tensioner pulley replacement, refer to Drive Belt Tensioner Replacement in Engine Mechanical.

Is the repair or replacement complete?

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Go to Step 30

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19
  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?

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Go to Step 20

Go to Step 21

20
  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?

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Go to Step 31

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21

Does the concern go away with the A/C clutch disengaged and the engine idling in PARK?

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Go to Step 22

Go to Engine Related Vibration in Vibration Diagnosis and Correction

22
  1. Recover the refrigerant.
  2. Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement .

Is the repair complete?

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Go to Step 31

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23

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

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Go to Step 24

System OK

24

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?

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Go to Step 18

Go to Step 25

25

Is the A/C compressor drive belt misaligned ?

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Go to Step 26

Go to Step 27

26

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?

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Go to Step 30

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27
  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?

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Go to Step 28

Go to Step 29

28
  1. Recover the refrigerant.
  2. Repair or replace the component which is causing the vibration/rattle concern as needed.

Is the repair complete?

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Go to Step 31

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29

Is the vibration/rattle coming from the A/C compressor internally?

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Go to Step 12

Go to Engine Related Vibration in Vibration Diagnosis and Correction

30
  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?

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Go to Step 2

Go to Control Assembly Description in HVAC Systems -- Manual

31
  1. Evacuate and charge the refrigerant system.
  2. Leak test the refrigerant system. Refer to Leak Testing .

Are the actions completed?

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Go to Step 32

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32

Recheck for the presense of the A/C system noise.

Is the A/C system noise still present?

--

Go to Step 2

Go to Control Assembly Description in HVAC Systems -- Manual