Sparking or arcing inside a microwave cavity is one of the clearest “stop using it now” signals among any appliance fault, and it’s worth understanding exactly why, rather than just powering through a cycle to finish reheating something.
Turn It Off and Unplug It
At the first sign of sparking, stop the cycle immediately, open the door, and unplug the unit rather than simply letting the current cycle finish. Continuing to run it risks damage to the magnetron and, in some cases, a genuine fire hazard.
The Most Common Cause
Metal utensils, twist ties, or even certain decorative patterns on dishware (some contain trace metallic pigment) left inside the cavity are the single most common cause, and removing the item usually resolves it completely.
When It’s Not About What Was Inside
If sparking happens with nothing metallic inside, a damaged waveguide cover — the small panel on the cavity’s interior wall, often near the top — is a frequent cause, since it can absorb moisture and grease over years of use and begin arcing on its own.
Don’t Attempt This Repair Yourself
Microwaves store high-voltage energy internally even when unplugged, which makes this a genuinely dangerous appliance to open without training. Visit our Kenmore microwave repair page for a technician who can inspect it safely.