[Guitarpicr]

Could be a thrown balancing weight or loose set screw as mentioned above. About 3 years ago we had a mud dabber make house in the a/c squirrel cage wheel. I was able to get it out from below with a long thin blade screwdriver & a small wire brush. Spraying it with some water helped out after most of the mud was removed to clean the blades. Problem solved. Make sure to wear your safety glasses for this job & put down a drop cloth below. I think they got in thru the dump vent which we have since kept closed. Hope u find the problem & it's an easy fix.