When Microwaving food, the display panel would seem to act normal, but the typical microwave sound would be absent. No microwave action would occur. Eventually an F5 code would display. Problem was the upper door switch. Found it by opening up the cabinet, removing the display panel (1 screw and a couple of plugs) and testing all three micro switched with a meter. Two switches are for the door and one for some kind of ventilation flap. They are all in the same area. Go to YouTube to see how to test and replace these switches. This model Kennmore Elite is made by LG.