This microwave micro switch is normally open and 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 will need to be replaced. The micro switch is in the latch board section and 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.