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Check the fan.............it may be locked up from "bugs" or something else. If that turns freely then take the bulb out and try it again. It might be the switch is shorted out. Get back to me if you need more once you check these out as all follow ups are included in our fee.
This can also be caused by a wire that is cut or pinched during construction. You may have to take the control panel off and insect that part carefully. IF you think mice may have gotten into the unit, they can be quite destructive and love to chew up wiring.