This motor wears out about 90,000 miles or that is the bearings wear out.
You have 2 options:
1. Replace the whole unit. $300.
2. Replace just the motor. $100.
I was advised that the squirrel fan was very difficult to remove off the shaft so the alternative was to purchase the complete unit.
Not true. The fan can be easily removed as follows:
1. Pull the complete unit out by disconnecting wires, removing the 2 bolts holding the unit to motor and undo the hoses that are connected.

2. Remove all the screws that hold the unit halves together and split the case.

3. Remove 2 bolts that hold the motor in and pull motor and fan out of the unit.
4. With the motor hanging down, support the fan by setting the bottom edges on 2 2X6's.
5. Take a punch and tap the motor shaft until the motor drops out.

6. Tap the fan onto the shaft of the new motor, put back together and install.
The fan is a pressed fit on the shaft. Put it all back together, install and viola.
Save yourself a couple hundred bucks.
Need help, e-mail me at benstaples@voyager.net