Were you sent here from Symptoms or another diagnostic table?

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Go to Symptoms - HVAC Systems - Manual

or

Go to Symptoms - HVAC Systems - Automatic

1. Sit inside the vehicle.
2. Close the vehicle doors and windows.
3. Turn ON the ignition, with the engine OFF.
4. Cycle the auxiliary blower motor through all of the speeds and modes in order to determine where and when the noise occurs.

Is a noise evident during auxiliary blower operation?

Go to Step 3

Go to Step 10

Does the noise vary with the auxiliary blower speed?

Go to Step 4

Go to Step 5

Inspect for excessive vibration at each auxiliary blower motor speed by feeling the auxiliary blower case.

Is excess vibration present?

Go to Step 5

Go to Step 10

1. Remove the auxiliary blower motor. Refer to Auxiliary Blower Motor Replacement .
2. Inspect the auxiliary blower motor for deposits of foreign material.

Did you find foreign material on the auxiliary blower motor?

Go to Step 7

Go to Step 6

Inspect the auxiliary blower motor for the following conditions:

Did you find any of these conditions?

Go to Step 8

Go to Step 9

Remove the foreign material.

Is the action complete?

Go to Step 10

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Replace the auxiliary blower motor. Refer to Auxiliary Blower Motor Replacement .

Is the action complete?

Go to Step 10

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Install the auxiliary blower motor. Refer to Auxiliary Blower Motor Replacement .

Is the action complete?

Go to Step 10

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Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Step 2