Quick Answer
Sparking usually comes from a damaged waveguide cover or metal in the cavity, while loud buzzing often points to a failing magnetron or fan. Unplug it if you see sparks. Microwaves hold high voltage, so internal repairs are a job for a local technician.
Sparking inside a microwave usually comes from a damaged waveguide cover or stray metal in the cavity, while loud buzzing often points to a failing magnetron or cooling fan. One of these you can sometimes fix; the other is strictly a pro job. Here is how to tell them apart.
Sparks vs buzzing
Sparks, or arcing, are bright flashes inside the cavity. Buzzing or grinding is a sound, usually from a worn part. They have very different causes, so treat them separately.
Quick, safe things you can check
- Remove any metal, foil, or dishes with metallic trim.
- Inspect the small waveguide cover on the cavity wall for burn marks.
- Wipe up food splatter, which can arc when it overheats.
If sparks continue after that, stop and unplug it.
Why microwave internals are not a DIY job
A microwave's capacitor can hold a dangerous high-voltage charge even after it is unplugged. The FDA advises leaving internal microwave service to qualified technicians for exactly this reason. If the noise sounds mechanical, our appliance noise guide can help you describe it.
Repair or replace?
Built-in and over-the-range units are usually worth repairing; a basic countertop model may not be. To decide, get connected with a local Fairfield technician or see our microwave repair page.
Frequently asked questions
Is a sparking microwave dangerous?
It can damage the unit and, rarely, start a fire. Unplug it and stop using it until the cause is found.
Why does it buzz only when running?
That points to a part under load, often the magnetron or fan, which a technician can test.