The door interlock switch, also known as a micro switch, works in conjunction with your microwave operation. The switch will prohibit the microwave from starting when the microwave door is open. If your microwave won’t turn on or there is no heat, you may need to replace the switch. This part is a little over an inch long, black in color with a red dot and is sold individually. This is a genuine OEM part. Please remember to disconnect the power before starting your repair.