microwave sparking and burning smell(5 Causes and Fixes)

If you own a microwave then you may have experienced sparking and burning with the microwave. Sparking may cause a lot of people to panic and even be weary of a looming fire hazard.

Due to its nature of using high voltages, a microwave will always be susceptible to sparking. This should assure you that most microwave problems are fixable and do not warrant a complete replacement of the appliance.

Most microwave sparking and burning smell problems may be traced to the following problems.

  1. Old Microwave Racks
  2. Faulty Diodes
  3. Faulty Magnetron
  4. Metal in Microwave
  5. Damaged Waveguide Cover

Old Microwave Racks

Microwave racks are made of metal that has been coated with a thin layer of plastic. Metals in a microwave will spark. To fix this you should:

  • Check the microwave racks for scratches
  • Replace the microwave rack

Faulty Diodes

A faulty microwave diode is the main problem that causes sparking and a burning smell in a microwave. Microwave diodes are responsible for the generation of the high voltage in the magnetron that powers the microwave.

Damaged diodes are easy to detect by using a multimeter to check for continuity. A diode should allow current to pass through in only one direction. The microwave diode is located next to the magnetron. Here are the steps you can take to test the diode.

  • Unplug your microwave from the power source.
  • Unscrew the backpanel to access the main electronics
  • Discharge the main capacitor to get rid of any residual charge left in the it.(Very Important). A microwave’s capacitor can hold enough charge to cause fatality in a human being.
  • Locate the main diode. This is a large black, round component with leads in both ends and a white/grey band on one end.
  • Set your multimeter in continuity mode and probe both leads with the negative and positive probes. Reverse the polarity of the probes and repeat again
  • If there is continuity in both cases or there in no continuity at all then the diode is damaged
  • A functional diode will have continuity in one direction only.

If the above test confirms a damaged diode you may replace the diode yourself or take it to a repair shop. If you plan to replace the diode yourself, then find the diode serial to order a similar one.

Faulty Magnetron.

The magnetron is the most important component in the microwave. A faulty or damaged magnetron will most likely render the microwave non-functional. Sparking in the microwave due to a magnetron failure may be an early indication that your microwave is likely to fail entirely in the future.

As with all other electronics a magnetron can also be replaced but you must first be able to diagnose it. You can follow the steps outlined below to check for a faulty microwave.

  • Unplug your microwave from the power source.
  • Unscrew the backpanel to access the main electronics.
  • Discharge the main capacitor to get rid of any residual charge left in the it.(Very Important). A microwave’s capacitor can hold enough charge to cause fatality in a human being.
  • Unscrew the magnetron for easier diagnosis.
  • A faulty magnetron can be probed for its resistance to determine its state.
  • Set you multimeter to ohms state.
  • Use the multimeter probes on both leads of the magnetron.
  • A reading of less than 1 ohm is an indication of a broken or non-functional magnetron filament.
  • Set the multimeter to the highest resistance testing setting.
  • Place one of the probes on the magnetron casing and the other on either of the magnetron leads
  • A functional magnetron should give you an “OL” or “Open Line” reading.
  • You may buy a replacement for the magnetron if the above test proves that it is damaged.

Metal in Microwave

You may have noticed warnings in your user manual of not to put metal in a microwave. Ever wondered why?

Any metal that you put in a microwave will result in sparking. This effect is more pronounced in metal objects with sharp points.

Cleaning you microwave with non metallic scrubbers should be a common practice. Avoid metallic scrubbers like steel wool as even tiny metal shavings will still cause sparking.

Damaged Waveguide Cover

Wave guide covers are the necessary component in your microwave that is responsible for evenly distributing the microwave energy from the magnetron. The waveguide cover is visible as a small square panel that is placed inside your microwave.

The waveguide cover should always be clean. It is important to repeat that a non metallic scrubber should always be used to clean the inside of your microwave. Food particles stuck on the wave guide cover may spark as the burnoff.


Can a sparking microwave be fixed?

Yes, a sparking microwave can be fixed as long as the underlying problem has been identified. Use our guide above to diagnose your problem and fix your microwave. There is no need to entirely dispose of your microwave if you can fix it. This also reduces your waste and carbon footprint.

What would cause a microwave to spark?

As identified in this post you may have 5 possible culprits namely:

  • Old Microwave Racks
  • Faulty Diodes
  • Faulty Magnetron
  • Metal in Microwave
  • Damaged Waveguide Cover

Be sure to identify the cause and rectify on it.

What to do if your microwave smells like it’s burning?

Your first option should be to clean out your microwave. If the problem persists and you are able to safely diagnose the problem, Proceed with the guide above and fix it or take it to repair shop.

What are the signs that a microwave is going bad?

Sparking and a burning smell are the first tell tale signs that your microwave is going bad. Other signs may be a non-functional keypad, Excessive humming, microwave not heating things up and its age(old appliances tend to wear out and need replacement)

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