My-microwave-stopped-heating-up-food, when your microwave turns on but does not heat up, it may mean the door switch is broken. the door switch signals other microwave components to supply power when closed, and to stop heating when open. the door switch can also be called an interlock switch.. The diode converts the a/c power output of the transformer to d/c, doubling the voltage to nearly 5,000 volts. this high voltage powers the magnetron to heat the food. if the diode burns out, the magnetron won’t receive enough voltage to operate, preventing the microwave from heating. when the diode fails, it is often visibly burned out.