I installed a replacement middle switch. There are three of them and one of them was shot. A simple multimeter or continuity checker will verify. My microwave had the chart for diagnosing wedged inside, next to the control panel. There are numerous videos available online that will help out if you need it. These switches are not very well constructed and within a month the new switch failed. Partspros sent me a replacement. They are not very expensive and shipping was about twice the cost. I learned my lesson and ordered a few extras to have on hand for when it goes out the next time.