DEFINITION: A constant air rush noise is typical of all heater systems. Some systems may be louder than others. If possible, inspect a similar vehicle in order to determine whether the noise is typical or excessive.

Did you perform the Function Test?

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Go to Step 2

Go to Function Test

1. Inspect all the electrical connections and the grounds for proper connections.
2. If a connection is doubtful, use a voltmeter in order to test for constant voltage at the blower motor.

Is the repair complete?

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Go to Step 3

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1. Sit in the vehicle with the doors and windows closed.
2. With the ignition switch in the ON position and the engine off, start the blower on the HI mode.
3. Select full COLD on the temperature rotary knob.
4. Cycle through the blower speeds, modes and temperature valve positions in order to find where the noise occurs.
5. Define the noise as one of the following types:

•	An air rush

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A whine

•	A tick/click

•	A squeal/screech

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A flutter

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A rumble

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A scrape

6. If possible, compare the noise with another vehicle of the same model in order to determine if the noise is typical.

Is the noise typically a flutter or a rumble that is constant at high blower speeds in certain modes, but can be eliminated at lower blower speeds?

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Go to Step 4

Go to Step 6

With the blower on HI, inspect the full HOT to the full COLD temperature positions in all modes.

Is the noise audible in all modes and in all temperature positions?

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Go to Step 5

Go to Step 8

1. Check the system for obstructions or foreign materials between the fan and the temperature valve.
2. Remove, repair, or replace the fan and the temperature valve as necessary.
3. Recheck the system for the noise.

Is the noise audible?

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Go to Step 3

Go to Function Test

Feel the blower armature in order to check for vibration of the motor and the fan at each blower speed.

Is the vibration excessive?

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Go to Step 7

Go to Step 10

1. Examine the blower fan for wear spots, cracked blades, or a cracked hub.
2. Examine the blower case for wear spots.
3. Repair or replace parts as necessary.
4. Recheck the system for the blower noise.

Did you find and correct the condition?

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Go to Function Test

Go to Step 11

Is the noise audible in all modes, but not audible in all temperature positions?

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Go to Step 9

Go to Step 12

1. Inspect the temperature valve seals.
2. Repair or replace the temperature valve seals as necessary.
3. Recheck the system for the noise.

Is the repair complete?

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Go to Function Test

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1. Remove the blower motor and fan assembly.
2. Check for foreign material at the orifice of the blower inlet.
3. Repair or replace the blower motor and fan assembly as necessary.
4. Recheck the system for the noise.

Did you find and correct the condition?

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Go to Function Test

Go to Step 7

1. Replace the blower motor and fan assembly.
2. Recheck the system for the noise.

Did you find and correct the condition?

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Go to Function Test

Go to Step 13

1. Check the ducts of the noisy modes for obstructions.
2. Remove any obstructions.
3. Check the seals of the suspected mode air valves.
4. Repair or replace the valves as necessary.
5. Recheck the system for the noise.

Is the repair complete?

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Go to Function Test

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Is the noise a click/tick or a whine?

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Go to Step 14

Go to Step 4

Replace the blower motor with a second new blower motor.

Did you find and correct the condition?

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Go to Function Test

Go to Step 15

Reinstall the original blower motor.

Is the repair complete?

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Go to Step 4

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