The secondary door switch, also known as a micro switch, works in conjunction with your microwave by monitoring the door latch position and sending communication to the electronic control board to let it know if the latch is open or closed. When the door is shut, the door switch will close to send power to the microwave to operate. If the microwave won’t start, the switch has failed, and the part will need to be replaced. You can test the switch for continuity. This part measures 1.5” L x .75” W. 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. Please disconnect power to the microwave before beginning the repair. This is a genuine OEM part.