Microwave Sparking Inside
You see sparks, arcing, or small flashes of light inside your microwave during operation. This is startling but usually has a simple fix — though some causes require immediate attention.
Step-by-Step Troubleshooting
Try these fixes before calling a technician
Stop the microwave immediately
Press stop and unplug the microwave. Sparking can damage the magnetron and interior walls if it continues. Open the door and let it cool before investigating.
Remove any metal objects
The most common cause of sparking is metal in the microwave — aluminum foil, a fork left on a plate, a twist tie, or a dish with metallic trim/paint. Even tiny amounts of metal (gold-rimmed plates, foil lining on containers) will arc.
Check the waveguide cover
Look inside the microwave for a small cardboard or mica panel on the side or top wall (the waveguide cover). If it's cracked, burned, or has food splatter baked onto it, it can cause arcing. This cover is inexpensive and usually replaceable — check your model for the right part.
Inspect the interior walls
Check the walls, ceiling, and floor of the microwave interior for peeling paint, rust, or burn marks. Damaged spots where the metal is exposed will spark. If the interior coating is peeling, the microwave may need replacement.
Check the turntable and rack
A broken turntable support or a metal rack that's touching the walls can cause arcing. Make sure the turntable ring is seated properly and not cracked. Metal racks (on convection microwaves) must be used correctly per the manual.
When to Call a Professional
If sparking continues after removing metal and replacing the waveguide cover, or if you see burn marks on the interior, the magnetron or high-voltage components may be damaged. Do NOT open the microwave cabinet — the capacitor holds lethal voltage even when unplugged.
West Metro Appliance Repair has completed 521 microwave repairs across 70+ Twin Cities communities. Our technicians see this exact problem regularly and can diagnose it quickly.
Microwave Repair Service
Factory-certified microwave repair across 70+ Twin Cities communities.