GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 1998 🢒 Cutlass 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Noise Diagnosis

Step

Action

Value(s)

Yes

No

1

Inspect the following components for proper connections:

    • All of the electrical connections
    • All of the grounds

Are any of the connections faulty?

--

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 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 conditions:
    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

Is the noise consistent with the following conditions?

    • Constant at high blower speeds with some door combinations
    • May be eliminated at lower blower speeds
    • May be eliminated with other door combinations
    • Sounds like a flutter or rumble

--

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

Does the noise occur in ONLY ONE of these 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 system operate properly?

--

System OK

Go to Step 8

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.

Is the repair 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.

Is the repair 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

Go to Step 16

15

Repair or replace the components as needed.

Is the repair complete?

--

System OK

--

16

Inspect for noise consistent with one or more of the following conditions?

    • Constant but lessens with blower speed reduction
    • Occurs only during start-up
    • Occurs intermittently
    • Occurs at cold ambients and low blower speeds
    • Sounds like one of the following noises:
       - 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 following 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

--

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.