Why is My Microwave Sparking? (And What to Do)

Seeing sparks or "lightning" inside your microwave while heating food is terrifying. While it looks like your appliance is about to explode, the issue is often fixable. However, you must turn off and unplug the microwave immediately to prevent permanent damage or fire.

Top 4 Causes of Microwave Sparking (Arcing)

1. Metal Inside the Microwave

This is the most common cause. Even a tiny piece of aluminum foil, a fork left on a plate, or plates with metallic/gold rims will cause electromagnetic waves to bounce off them, creating sparks.

2. Burnt Waveguide Cover

Look inside your microwave on the right or left wall. You will see a small, square piece of cardboard or plastic. This is the waveguide cover. If food splatters onto it and burns, the carbonized food will act like metal and cause sparking. If it looks burnt or has a hole in it, it needs replacement.

3. Carbonized Food Splatters

If you don't clean your microwave regularly, old food splatters on the walls or ceiling will continue to cook, eventually turning into carbon. Carbon arcs just like metal when exposed to microwaves.

4. Faulty Diode or Magnetron

If the inside of your microwave is perfectly clean, the waveguide cover is intact, and there is no metal, the sparking is likely coming from a shorted high-voltage diode or a failing magnetron (the part that generates the heat).