If the fan will not run when you directly apply 12 volts to it (bypassing all the switches and relays--it may be the brushes are not making contact with the armature. You CAN disassemble it, clean the armature, relube the bearings, and go for another 20 years. These fans are hell bent for stout, but for some reason the brushes will hang up or fail to make contact (the armature gets dirty from leaking bearing lube maybe?) I had one on which the 'foam' seal on the front under the flan blade dissolved/crumbled and jammed the bearig. Cleaned things out (was 10 years old down here in the hell city of Houston and looked like new inside), replaced foam seal with one cut from christmas decoration felt, regreased bearing, went another 10 years fine.