Remove microwave outer cover. Turn on side & locate the upper & lower door switches. Better to replace in pairs even if one is ok. Remove the wire harness to each switch. Then replace switch and re connect the wire harness. Re attach outer cover and test to see if that solved the problem. If so then well done!!
First I disconnected the power and opened the door. Then I removed the top screws holding the top vent louvers, then removed the screw at the top of the touch pad. The touch pad removes by sliding up slightly then tilting top out. I unscrewed two screws holding the door latch assembly. Press the tab to remove and replace switch. Reconnect wires, reseat latch mount by placing top bracket tab in place first, allign and secure with screws. Reseat touch pad by placing bottom tabs in first, tilt forward and press up to seat top tabs, secure with top screw. Secure vent louver screws, plug in and watch your microwave work again.
I unplugged it, removed the outer shell with torque bits and a screwdriver, drained the main capacitor, and began debugging the circuit with my fluke multimeter, found the bad primary interlock, googled the part number, ordered the part, received it in 2 days, replaced the interlock in about 2 minutes, and put the cover back on. Fixed. Saved me about $200 over buying a new unit and was grateful for partselect's great service.
