We have a 35U. The fan was making a very loud noise. It seemed that something was stuck in the fan blades. This was about 4 months back and I knew that we would want to use it in the winter. In our coach the front passenger basement compartment has the hot water tank to the right. Behind that there is a metal duct that can be removed with 4 screws. (It is a bit dificult to get to the back two screws) It contains a squarel cage motor and fan. You then can unplug the electrical conection which will alow you to remove the complete unit from the coach. I would test the conection with a test light to confirm that you have power to the fan motor. You may need to replace the motor then reinstall. My fan blade had shifted to one side causing it to scrub the cover. Be sure to check the fues if you dont have power to the plug. Also before you remove the motor, spin the fan to see if it moves freely.
hope this has been helpful to you
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2013 Winnebago Tour 42QD