GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1998 🢒 Grand Am 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Noise Diagnosis

Important: A constant air rush noise is typical of all systems with the blower in the HIGH position. Some systems and modes (usually the DEFROSTER mode) are more noticeable than other systems and modes. Compare the noise with the noise in another vehicle (the same model, if possible) in order to determine if the noise is normal.

Step

Action

Value(s)

Yes

No

1

Inspect all of the electrical connections and all of the grounds.

Is the condition of any of the connections in doubt?

--

Go to Step 2

Go to Step 4

2

Use a voltmeter in order to inspect for constant voltage at the blower motor.

Is the voltage constant?

--

Go to Step 4

Go to Step 3

3

Repair any connections as needed.

Are the repairs complete?

--

Go to Step 4

--

4
  1. Sit in the vehicle.
  2. Close all of the doors and the windows.
  3. Turn the ignition switch to the ON position. Do not turn on the engine.
  4. Set the blower control to the HIGH position.
  5. Set the mode control to the VENT position.
  6. Set the temperature control to the FULL COLD position.
  7. Cycle through the following settings:
    8. • The blower speeds
    • The modes
    • You may have to start the engine occasionally in order to change the mode
    • The temperature valve positions
  8. Determine the origin of the noise.
  9. Determine the type of noise:
    10. • Air rush (see note)
    • Whine
    • Tick or click
    • Squeal or screech
    • Flutter
    • Rumble
    • Scrape
  10. Determine if the noise is consistent within the following conditions:
    11. • The noise is constant at high blower speeds with some door combinations.
    • The noise is not present when the blower speed is low.
    • The noise is not present when other door combinations are present.
    • The noise sounds like a flutter or a rumble.

Is the noise consistent with the above conditions?

--

Go to Step 5

Go to Step 16

5
  1. Set the blower control to the HIGH position.
  2. Set the temperature control to the FULL HOT position and the FULL COLD position in the following modes:
    3. • DEFROST
    • HEATER
    • VENT
    • Listen for the noise.

Does the noise occur in ONLY ONE of the above modes?

--

Go to Step 6

Go to Step 10

6

Inspect the ducts for obstructions or foreign materials.

Are the ducts obstructed?

--

Go to Step 7

Go to Step 8

7

Remove the obstruction or foreign material from the ducts.

Does the noise persist?

--

Go to Step 8

System OK

8

Inspect the valve seal.

Is the valve seal in need of repair or replacement?

--

Go to Step 9

--

9

Repair or replace the valve seal as needed.

Are the repairs complete?

--

System OK

--

10

Does the noise occur in all of the modes but not all of the temperature positions?

--

Go to Step 11

Go to Step 13

11

Inspect the temperature valve seals.

Are the valve seals in need of repair or replacement?

--

Go to Step 12

--

12

Repair or replace the valve seals as needed.

Are the repairs complete?

--

System OK

--

13

Does the noise occur in all of the modes and in all of the temperature positions?

--

Go to Step 14

System OK

14

Inspect the system for obstructions or foreign materials between the fan and the temperature valve.

Are any components in need of repair or replacement?

--

Go to Step 15

--

15

Repair or replace the components as needed.

Are the repairs complete?

--

System OK

--

16

Listen for noise that is consistent with one or more of the following conditions:

    • The noise is constant but lessens with blower speed reduction.
    • The noise occurs only during start-up.
    • The noise occurs intermittently.
    • The noise occurs at cold ambient temperatures and low blower speeds.
    • The noise fits one of the following descriptions:
       - A whine
       - A tick or a click
       - A flutter
       - A scrape
       - An objectionable squeal or screech

Is the noise consistent with one or more of the above conditions?

--

Go to Step 17

--

17

Inspect for motor vibration or fan vibration at each blower speed by feeling the blower motor.

Is the vibration excessive?

--

Go to Step 20

Go to Step 18

18
  1. Remove the blower motor and the fan assembly. Refer to Blower Motor and Fan Replacement .
  2. Inspect for foreign material at the orifice of the blower inlet.

Was an obstruction found?

--

Go to Step 19

Go to Step 20

19

Repair or replace the components as needed.

Is the repair complete?

--

System OK

--

20

Replace the motor and the fan assembly. Refer to Blower Motor and Fan Replacement .

Is the repair complete?

--

System OK

--