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Fix a microwave that sparks

We'll remove metal and foil, clean the cavity, inspect and replace the waveguide cover, or tell you when to call a pro.

Troubleshooting · Home appliances
10–25 min
What you'll need
  • Damp cloth and mild soap (for cleaning)
  • Replacement waveguide cover (if damaged—order by model number)
  • Screwdriver (if the cover is screwed in)
Step 1 of 8

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Steps

Goal: Stop the microwave, remove metal and foil, clean the cavity, inspect and replace the waveguide cover, or call a pro.

  • Stop the microwave immediately when you see sparks. Do not let it run—arcing can damage the magnetron or start a fire.
  • Good: You stopped it—proceed to Remove metal and foil.
  • Bad: You let it run—unplug and wait for the interior to cool before inspecting.

Remove metal and foil

Goal: Eliminate the most common cause of sparks—metal inside the cavity.

  • Check for aluminum foil, metal utensils, foil-lined packaging, or dishes with gold or metallic trim. Metal reflects microwaves and causes arcing.
  • Remove all metal and foil. Confirm the cavity is clear.
  • Good: Metal was present—remove it, then proceed to Clean cavity. Bad: No metal—proceed to clean and inspect the waveguide cover.

Clean cavity

Goal: Remove food splatter and grease that can burn and arc.

  • Unplug the microwave. Wipe the interior with a damp cloth and mild soap. Pay attention to the ceiling and the area around the waveguide cover.
  • Dry the cavity. Confirm no visible splatter or grease remains.
  • Good: Cavity is clean. Proceed to Inspect waveguide cover. Bad: Grease or food still present—clean again.

Replace waveguide cover

Goal: Fix a damaged waveguide cover that exposes metal and causes sparks.

  • Locate the waveguide cover—a flat plastic or mica panel on the ceiling or side wall of the cavity, often rectangular with small holes or slots.
  • Check for burns, cracks, peeling, or discoloration. A damaged cover exposes metal underneath and causes sparks.
  • If damaged, order a replacement by model number from the manufacturer or an appliance parts supplier. Remove the old cover (usually screws or clips) and install the new one flush. Do not run the microwave without a waveguide cover.
  • Good: You replaced the cover. Test with a cup of water—no sparks. Bad: Cover is intact but sparks persist—check for rust or call a pro.

When to get help

Do not use a microwave that sparks. Arcing can damage the magnetron or start a fire.

Call an appliance technician if:

  • Sparks continue after removing metal, cleaning the cavity, and replacing the waveguide cover.
  • The cavity has heavy rust or holes.
  • You are not comfortable replacing the waveguide cover.

Verification

  • No sparks when running the microwave with a cup of water for one minute.
  • No metal, foil, or metallic trim inside the cavity.
  • The waveguide cover is intact with no burns, cracks, or peeling.
  • The cavity is clean with no visible food splatter or grease.

Escalation ladder

Work from the device outward. Stop when the problem is fixed.

  1. Stop and remove metal Stop the microwave immediately. Remove all metal, foil, and metallic trim.
  2. Clean cavity Wipe food splatter and grease from the cavity and around the waveguide cover.
  3. Replace waveguide cover Inspect and replace the waveguide cover if burned, cracked, or peeling.
  4. Check for rust Inspect the cavity for rust or corrosion; heavy rust may require replacement.
  5. Call a pro Sparks continue after these steps—call an appliance technician. Do not use a sparking microwave.

What to capture if you need help

Before calling support or posting for help, have these ready. It speeds everything up.

  • Microwave brand and model
  • Whether metal or foil was present
  • Waveguide cover condition (intact, burned, peeling)
  • Whether cleaning and replacement resolved the sparks
  • Steps already tried

Did you see sparks inside the microwave?

Sparks indicate metal, a damaged waveguide cover, or food debris. Stop the microwave immediately.

Stop the microwave as soon as you see sparks. Do not let it run. Good: you stopped it—proceed to remove metal. Bad: you let it run—unplug and wait for it to cool before inspecting.

Yes No

You can change your answer later.

Is there metal, foil, or metallic trim inside?

Metal, aluminum foil, foil-lined packaging, and dishes with gold or metallic trim cause sparks.

Check the cavity for aluminum foil, metal utensils, foil-lined packaging, or dishes with metallic trim. Remove all metal. Metal found: remove it, clean the cavity, test with a cup of water. No metal: proceed to clean and inspect the waveguide cover.

Yes No

You can change your answer later.

Remove metal, clean cavity, and test

Remove all metal and foil. Clean food splatter and grease from the cavity. Test with a cup of water for one minute. Good: no sparks—fix complete. Bad: sparks return—inspect the waveguide cover.

Done

Is the cavity clean and the waveguide cover intact?

Food debris and a damaged waveguide cover can cause sparks.

Clean the cavity with a damp cloth and mild soap. Inspect the waveguide cover for burns, cracks, or peeling. Dirty: clean and test. Cover damaged: replace the waveguide cover. Cover intact: check for rust.

Yes No (dirty or damaged)

You can change your answer later.

Replace waveguide cover and test

Replace the waveguide cover with an exact match (order by model number). Install it flush with no gaps. Test with a cup of water. Good: no sparks—fix complete. Bad: sparks return—check for rust or call a pro.

Done

Is there rust or corrosion in the cavity?

Rust on metal surfaces can arc. Heavy rust or holes mean the cavity is compromised.

Inspect the cavity for rust or corrosion. Light surface rust may be cleaned; heavy rust or holes mean replace the microwave or call a pro. Rust found: clean if light, or replace/call pro if heavy. No rust: sparks persist—call a pro.

Yes No

You can change your answer later.

Clean light rust or replace microwave

Light surface rust: clean with a damp cloth and test. Heavy rust or holes: the cavity is compromised—replace the microwave or call a technician. Do not use a microwave with a badly rusted cavity.

Done

Call a technician

Call an appliance technician if sparks continue after removing metal, cleaning the cavity, and replacing the waveguide cover. Do not use a microwave that sparks—it can damage the magnetron or start a fire.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Why does my microwave spark?
Sparks usually come from metal (foil, utensils, metallic trim on dishes), a damaged or dirty waveguide cover, or food debris. Metal reflects microwaves and causes arcing. A burned or peeling waveguide cover exposes metal underneath and arcs.
Can I fix a sparking microwave myself?
Yes. Most sparking is caused by metal or a dirty or damaged waveguide cover. Remove metal, clean the cavity, and replace the waveguide cover if it is burned or peeling. Unplug before any repair. Call a technician if sparks continue after these steps.
When should I call a technician for a sparking microwave?
Call an appliance technician if sparks continue after removing metal, cleaning the cavity, and replacing the waveguide cover. Do not use a microwave that sparks—it can damage the magnetron or start a fire.

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