It all started when my daughter used he microwave as a timer, and ran it empty. I checked all the fuses with a meter and found one that was open. It is on the back wall behind the control pad. I have looked at the exploded diagram and for the life of me cannot see what part it is. I ordered a part here, then tried my local shop. Both look like the same part, but have different part numbers. When I hook the new parts up and plug it back in, the exhaust fan stays on. You can turn it up to high, then back to low, but not off. The microwave works. I took the wires off and jumped them together and everything works just fine. I'm starting to get pretty frustrated.