I see sparks inside my microwave.

Investigate these areas if there are sparks (also called arching) inside your microwave:

Internal Cavity

Check the internal cavity of your microwave. Any food that has splattered or dripped into the microwave can continue to cook, causing sparks inside your microwave. This also applies to grease accumulating on the ceiling. Give your microwave a thorough cleaning.


Microwave energy could be concentrating in one area of your microwave, instead of distributing evenly throughout the unit, causing burning and sparking. This will happen if your microwave stirrer is not working. There are two reasons why your stirrer would not be working: either the fan motor is broken, or the stirrer belt is broken.

High Voltage Diode

The high voltage diode could be shorted or opened. You will have to test it with your ohmmeter, and if need be, replace it.

CAUTION: Your microwave oven is capable of giving you a serious electrical shock, even when it is unplugged. We strongly suggest you seek the assistance of an appliance repair technician when conducting any microwave oven repair.