In response to Shannah Zinkievich's musical chair movement that won't start every time [161022 MMDigest], before you send it out to be serviced, try oiling it.  The most important point to oil is where the worm mates with the worm gear (the worm is the shaft with the fan blades on it).  Put a tiny bit of oil on each of the bushings (the holes that hold the gear axles).  Too much oil will only be dragged out of the hole by gravity, so use it sparingly.

Good luck!

Nancy Fratti - Nancy Fratti Music Boxes
Canastota, New York, USA