The microwave primary door switch, also known as a micro switch, is normally open. When the door is shut, the door switch will close to send power to the microwave to operate. If the microwave won’t start, then the switch has failed, and the part will need to be replaced. The micro switch is in the latch board section and monitors the position of the door. This part measures 1.5” L x .75” W NOTE: Due to the high voltage capacitor in the microwave, it can retain a lethal electrical charge, even when unplugged. It is suggested to have a service technician install the part. This is a genuine OEM part. Please disconnect the power to the microwave before beginning the repair.