What's going on
Microwaves heat food by sending energy into a metal-lined cavity. Bare metal in the wrong place makes that energy arc, which shows up as sparks, snaps and sometimes a burning smell. The obvious culprits are foil, twist ties, metal-trimmed dishes and utensils left in a bowl. A less obvious one is the waveguide cover, a small panel, often mica, on an inside wall where the energy enters. Grease and food splatter build up on it, char and then spark.
Other causes include interior paint that has chipped and exposed bare metal, and metal racks used in a model that wasn't designed for them. Running a microwave empty is also hard on it, because the energy has nothing to go into. Sparks that keep happening can burn through the waveguide cover and damage parts behind it.
What you can check in five minutes
- Stop the microwave and unplug it, or switch off its breaker if it's built in or over the range.
- Remove anything metal, including dishes with metallic trim or paint.
- Look at the waveguide cover. If it's dirty, wipe it gently with a damp cloth and let it dry.
- If the cover is burned through or cracked, check your manual. On many models it's listed as a replacement part.
- Look for chipped paint or rust spots inside the cavity, especially around the floor and the door.
- Don't run it empty to test it. Use a cup of water if your manual allows a test.
- Never open the outer housing. Microwaves store high voltage inside even when unplugged.
Rent, own or co-op: who handles it?
If the microwave came with the apartment, stop using it and tell the super. A sparking unit is a fire risk, not something to live with. Countertop units you bought are usually yours to deal with. Check your lease or ask your building if you're unsure who owns it.
What a technician will look at
- •Waveguide cover condition and the area behind it
- •The cavity interior and the door surfaces where they meet
- •The stirrer or antenna system, depending on design
- •The magnetron and high-voltage parts, by a trained technician only
- •Door switches and the door seal
Andre's field note: A grease-caked waveguide cover is behind a lot of the sparking I'm called about, and cleaning it, then keeping metal out, usually ends the problem. Burn marks that go past the cover are a different story. That's work for a microwave technician. Odd crackling can also come from debris, so if you've had pests inside appliances, mention it when you call.
Sparks or a burning smell? Unplug it, then call ProFix NYC at (929) 699-8358.