Sparks Inside a Thermador Microwave: Stop and Unplug

Why sparks are never cosmetic

Seeing sparks or flashes within the cooking chamber of a microwave or speed oven is never a trivial matter. The cause is typically metal touching something it should not, or interior damage, so the unit should be inspected by a professional before any further use. Carrying on with an arcing unit risks harming the magnetron further and creating a fire hazard.

What to do at once

1. Stop the cycle and open the door only once everything is quiet.
2. Pull the plug, or flip the breaker if the unit is hard-wired into the cabinet.
3. Take out any metal, foil, or dish with metallic trim.
4. Look for a burn mark or scorched spot inside, and note where it is.
5. Leave it off until it has been inspected.

Why not test it once more

It is tempting to run a short cycle with a cup of water to see whether it happens again. Resist that. If the interior is damaged, each cycle can worsen it, and what began as a small repair can grow into a larger one.

What the inspection covers

We examine the cavity walls, the area where the waveguide cover sits, the door seal, and the magnetron, then explain what we found before we start any work. Read more about what we handle on our microwave repair page.

Do not try to scrape or paint over a scorched spot yourself. The coating inside is part of how the cavity holds energy, and a damaged patch is something we need to see in place.

Once it is unplugged, book a diagnostic visit. We give you a written price first, and the work comes with a 30-day workmanship warranty.