Had a fuse issue with a Jenn-Air the other day, 3 tech's were out before me and none bothered to check the switches which had obvious scorch marks. Replaced them new fuse and the customer now has a micro after over a year and a half.
Great idea with the trip switch! Not really the way I like to troubleshoot but if it's a tough one I can't find that would be a perfect way to narrow down the problem. How did you make it?