Microwave Sparking or Arcing: What to Do

Quick answer

Microwave sparking, also called arcing, is most often caused by metal inside: foil, a twist tie, a fork, or a dish with metallic trim. Built-up food splatter or a damaged interior coating or cover can also spark. Stop the microwave right away, remove any metal, and look for damage before using it again. This guide is for anyone who has just seen flashes or heard popping inside their microwave and wants to know what’s safe.

Safety first

• Stop it immediately. Press Stop or open the door as soon as you see sparks. Don’t let it keep running to “see what happens.”
• If something is on fire, keep the door closed. Turn the microwave off, and unplug it only if you can reach the plug safely. Keeping the door shut starves the fire of air. If it doesn’t go out quickly, leave and call 911.
• Never open the cabinet. Microwaves hold dangerous high voltage inside even when unplugged. Don’t remove the outer cover or any interior panel, and don’t poke anything into the vents or openings.
• Never tamper with the door latch or safety switches.
• Unplug before cleaning or inspecting inside, or switch off the circuit breaker for an over-the-range model whose plug you can’t reach.
• Stop using it if there’s damage. A scorched, chipped or burned interior, or a damaged door, means it should be checked before any further use.

Before you begin

Find your model number on the rating label, usually inside the door frame or on the back, and download the owner’s manual from the manufacturer’s support site. The manual shows what’s normal inside your microwave, which accessories are microwave-safe (some models come with a metal rack meant only for certain modes), and which parts, if any, the owner can clean or replace.

Think about what was inside when it sparked. Was there foil, a takeout container with a metal handle, a mug with gold or silver trim, or a spoon left in a bowl? The answer often points straight to the cause.

Possible causes

Things you can check yourself:

• Metal in the microwave: foil, twist ties, utensils, takeout containers with metal handles, or dishes with metallic paint or trim
• A metal rack used in a mode the manual doesn’t allow, or placed so it touches the walls
• Splattered food or grease stuck to the walls, ceiling or the waveguide cover (a small flat panel on an inside wall that covers the opening the microwaves come through)
• Certain foods that occasionally spark briefly, especially some dense or seasoned items, or very small amounts of food

Problems that need a technician:

• A burned, cracked or missing waveguide cover that your manual says isn’t user-replaceable
• Chipped or peeling interior paint or enamel, with bare metal showing
• Arcing that continues with nothing metal inside and a clean cavity
• A damaged door, door seal or hinges
• Any internal fault involving high-voltage parts

What to do after a microwave sparks

1. Stop and unplug. Stop the microwave, let it cool, and unplug it (or switch off its breaker) before you reach inside.
2. Remove all metal. Take out anything metallic, including foil, twist ties and utensils. Check dishes and mugs for metallic trim, including thin gold or silver bands. If your microwave came with a metal rack, check the manual to see whether it belongs in the mode you used.

   Was metal the cause? If so, and you see no marks or damage inside, the microwave may be fine. Go to step 5 to test it. If not, go to step 3.

3. Look closely inside with a flashlight. Check the walls, ceiling, floor and the inside of the door. Look for black or brown scorch marks, bubbling, chipped paint, bare metal or burn holes. Find the waveguide cover (your manual shows where it is) and look for burned spots, cracks or food stuck to it.

   Do you see damage? If the interior coating is chipped or burned, or the waveguide cover is damaged, stop using the microwave. Some manuals describe the waveguide cover as a part the owner can replace; follow your manual exactly if so. Otherwise, call a technician.

4. Clean any food splatter. If you only see food buildup, wipe the inside with a soft cloth and warm, soapy water, including gently over the waveguide cover. Don’t use scouring pads or harsh abrasives, which can damage the coating. Dry everything well.
5. Test carefully. Plug back in and run the microwave for a short time with a cup of water inside. Stay right there and watch.

   Any more sparks? If it runs quietly, you can go back to normal use while watching for any return of sparks. If it sparks again with nothing metal inside, unplug it and stop using it until a technician has looked at it.

6. Watch for related signs. A microwave that sparked and now doesn’t heat, or that smells of burning, likely has damage inside. See microwave not heating for what to know.

When to stop and call a qualified technician

Stop using the microwave and contact a technician if:

• It sparks again with no metal inside and a clean interior
• You see scorched, chipped or peeling interior paint, or bare metal
• The waveguide cover is burned or damaged and isn’t listed as user-replaceable in your manual
• The door, seal or hinges are damaged, or the door doesn’t close properly
• There was a fire inside, or you smell burning after it has cooled
• It stops heating, hums loudly, or trips the breaker

Contact the manufacturer’s service network through its support site, or a qualified appliance technician. If the microwave is old or badly damaged, replacing it may make more sense. See appliance warning signs for other times to stop using an appliance.

FAQ

Is it safe to use a microwave after it sparked?

If the sparks came from metal you removed and there’s no damage inside, it’s often fine. Test it with a cup of water while you watch. If it sparks again or you see damage, stop using it.

Why is my microwave sparking with no metal inside?

Food or grease stuck to the walls or the waveguide cover can spark, and so can a damaged interior coating. Clean it, inspect it, and if it still sparks, call a technician.

What is the waveguide cover?

It’s a small, flat panel on an inside wall that covers the opening the microwaves come through. Food splatter on it can burn and spark. Your manual shows where it is and whether you can replace it.

What should I do if there’s a fire in my microwave?

Keep the door closed, turn it off and unplug it if that’s safe. The fire usually goes out without air. If it doesn’t, leave and call 911, and have the microwave checked before using it again.

Can certain foods make a microwave spark?

Sometimes. Some foods spark briefly, often because of minerals or seasoning, especially in small amounts. If it happens, stop the microwave, cut or arrange the food differently, and check the interior. Browse more microwave guides for related issues.