My son and I ventured under the dash thinking a worn wire was grounding out and causing the fuse to blow, we had narrowed it down to this. Everything looked perfect, real clean. After checking all the connections I said let's try another fuse and SHAZAM!!, it works!! Runs on HI and LOW but I guess I'll leave well enough alone.

 

Don't argue with success. Probably was a loose connection.

 

It was probably a connection that was a little corroded. A lot of time all you have to do is pull a connector off and put it back on.

 

Low quality / defective fuses can often break near the ends, leaving the circuit open but 'looking' good. I have seen this several times.