By AFZ Appliance Repair. Published November 1, 2026.

Quick answer

Microwave running but food stays cold? See the few checks that are safe to do yourself, and why you should never open the cabinet, even when it is unplugged.

A microwave that runs but leaves food cold has usually lost power to the part that makes the heat. The FDA explains (opens in a new tab) that a device called a magnetron produces the microwaves. When it, or a part that feeds it, fails, the light and turntable can keep working as if nothing is wrong.

The safe checks

Make sure you started a cook cycle and not the timer. GE Appliances lists (opens in a new tab) this as a first check.
Open the door and close it firmly, so that the door's safety mechanisms engage.
Test with a cup of water for one minute. If the water stays cold, the microwave is not heating.
Plug it directly into a wall outlet. The U.S. Fire Administration (opens in a new tab) warns against using extension cords with major appliances.

Do not open the cabinet

GE Appliances offers no do-it-yourself repair advice for microwaves, for a clear reason. An internal high voltage capacitor can hold a charge even after the microwave has been unplugged. Do not remove the outer case, and do not try to test parts inside it.

When the door is the problem

The FDA says microwave energy will not leak from a microwave in good condition, but a damaged one may present a risk. Stop using it if the door hinges, latches or seals are damaged, or if the door does not open or close properly. Contact the maker for help if it is under warranty.

When to stop and call

Stop using the microwave if you see sparks you cannot explain, smell burning or hear a loud new buzz. Metal in the cavity causes sparks too, so check for foil or a metal rack first. Our microwave repair page lists more faults. If your unit is older, our guide on whether to fix or buy new can help you decide.