Why Does My Microwave Spark Inside?

If your microwave is sparking inside, the cause is usually metal inside the unit, a damaged waveguide cover, food buildup, or a failing internal component.

Sparks inside a microwave should never be ignored. While some causes are simple and harmless, others can damage the appliance if not addressed quickly.

Here’s what to check.

1) Metal Inside the Microwave

The most common cause of sparking is metal.

This includes:

• Aluminum foil
• Utensils
• Dishes with metallic trim
• Twist ties

Even small metal fragments can cause arcing.

Remove any metal objects and test the microwave again.

2) Damaged Waveguide Cover

Inside most microwaves is a small rectangular panel on the interior wall called the waveguide cover.

If this cover becomes:

• Burned
• Cracked
• Grease-soaked

It can spark during operation.

If you notice visible burn marks, the cover may need replacement.

3) Food or Grease Buildup

Old food splatters can carbonize and cause sparks.

Pay special attention to:

• The ceiling of the microwave
• The walls near the waveguide cover
• The turntable area

Thoroughly clean the interior with mild detergent and warm water.

4) Damaged Rack or Turntable Support

If your microwave has a metal rack and it is misaligned or damaged, it can cause sparking.

Remove the rack and test the unit without it.

5) Failing Diode or Magnetron

If sparking continues even after cleaning and removing metal objects, there may be an internal electrical problem.

Signs of a more serious issue include:

• Loud buzzing noises
• Burning smells
• Microwave not heating properly

Internal component repairs should be handled by a professional.

When to Stop Using the Microwave

Stop using the microwave immediately if:

• Sparking is frequent
• You see flames
• There is a strong burning odor
• The interior paint is peeling

Continued use could cause further damage.

Quick Recap

If your microwave is sparking inside, check:

• For metal objects
• The waveguide cover
• Food buildup
• Rack positioning
• Internal components

Many sparking issues are caused by simple cleaning or removal of metal items.