Microwaves are a great appliance to have around when leftovers need a quick zap of heat– but nothing is more shocking than when you hit start and find your microwave sparking. Not only is it a costly kitchen appliance, but installing a new one can become time-consuming if you have to detach it from a suspended position.

But don’t run off to the store just yet…

Some reasons a microwave might spark are easy to identify and solve. Other reasons why microwaves spark are a little more complex. If you’re looking for solutions, there are several key factors you’ll want to consider before replacing your appliance.

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Fixing a Sparking Microwave

Everyone knows how to use a microwave, but not everyone understands how complex (and sometimes potentially hazardous) it can be to fix some of the more complex issues. Microwaves generate an electromagnetic wave of energy that is pushed through the appliance and absorbed by the food, and that energy requires some safety measures.

Before You Begin

• Be cautious when handling your microwave and take precautions to prevent a bump or fall. This can further damage the appliance and cause more headaches.
• Make sure that your microwave is unplugged before examining any aspects of potential damage.
• Always remember that even an unplugged microwave is holding a potential shock internally. A pair of rubber gloves should be worn when working under the casing.
• Use an insulated screwdriver when unscrewing anything from the machine. More complex issues will require this tool to discharge specific areas.

Reason #1: Metal or Microwave Rack

Sparks fly when a microwave meets metal. If you see sparks, disrupting the process as quickly as possible is vital. Forgetting a misplaced fork or aluminum foil covering can happen. However, the longer your microwave sparks, the higher the risk of irreparable damage and potential fire.

When this becomes a problem: Avoiding metal in the microwave isn’t a hard lesson to learn. Even if you’ve never been told to avoid the combo, it’s a relatively quick and easy lesson to learn. If you’ve ever made the mistake of leaving aluminum foil over your food or left a utensil behind, you know how quickly sparks start occurring after hitting the start.

Additional Considerations: You may or may not utilize a microwave rack when operating your machine. If one is present, pay attention to the protective covering. Every microwave rack is wrapped to prevent the metal frame from causing problems. However, this metal frame can be compromised and leave the metal frame exposed.

How to fix: Always begin by diagnosing a microwave sparking by assessing the situation. Did you unintentionally leave behind a metal utensil? Is a microwave rack posing a risk? Believe it or not, these are the most common reasons someone might experience microwave sparking.

Reason #2: Waveguide Cover

A waveguide is vital to the functionality of your microwave as it provides the energy waves necessary to cook your food. Diagnosing a waveguide cover can sometimes be easier because the food might be heating inconsistently.

When this becomes a problem:

• Your microwave is heavily utilized and/or has experienced a significant tumble that knocked the waveguide loose.
• Your microwave is typically left with food on the inside and might go long periods without a deep cleaning.
• Your microwave recently experienced an explosion with food going everywhere.

Additional Considerations: Is your microwave subjected to a high amount of greasy foods or experienced more than a few explosions?

How to fix: 

1. Clean your microwave. Sometimes, food will build up on the outside of the safeguard and spark as it’s burned off. It’s possible a deep cleaning can solve the problem.
2. Know your model number. This will be required to order replacement parts.
3. Buy replacement parts. If you’re still experiencing sparking, the waveguide may be beyond hope. Look online for a replacement waveguide based on your model number.
4. Change the waveguide. Make sure you have some cleaning supplies on hand.
   • Remove the rivets or screws holding the waveguide in place.
   • Remove the cover.
   • Assess the cleanliness of your waveguide. It’s possible that the issue was caused by grease or dirty food particles. Clean the space before installing your new cover.
   • Fit your new waveguide into place by aligning the screw or rivet holes. Replace the screws or rivets.
   • Clean the new cover before running your microwave.

Reason #3: Diode

The diode works in tandem with the magnetron of a microwave to convert alternating and direct currents to increase the power and heat foods. Without a working diode, the magnetron cannot produce the energy to heat food.

When this becomes a problem: There are several factors that might cause the diode to begin sparking and cause additional problems. Common causes include a defective magnetron, a defective door switch, or even a faulty high-voltage capacitor.

Additional Considerations: A microwave emitting an electrical burning smell can be a direct indicator of a bad diode. Additionally, you might observe it is burnt, cracked, or even split into pieces. 

How to fix: A diode can pose potential problems for untrained individuals. High voltage and high current can be present even after unplugging the appliance.

• Remove the microwave plug from the outlet.
• A suspended microwave will need to be removed.
• Access the back panel and remove the screws. Do not touch any wires and wear rubber gloves for additional protection.
• Locate the capacitor (a small box with a black cylinder sticking out)
• Find the two metal prongs with wires running out of them.
• Using an insulated screwdriver, grasp the insulated handle (do not touch any metal) and slide the metal part against the metal prongs.
• Pay attention and listen for a snapping or clicking sound. This indicates you’ve successfully discharged the unit.
• Test the diode with a multimeter by setting it to Rx10,000 or higher. You will need to test the diode twice (switching the lead placement each time).
• A defective diode will provide identical readings from both ways.

Reason #4: Magnetron

Magnetrons are not typically an issue causing a microwave to spark. However, it’s possible that it can become an issue. A microwave without a functioning magnetron cannot produce energy to warm food.

When this becomes a problem: The age of your microwave can play a huge role in the workings of a magnetron. If your microwave is older, it’s more likely it could have stopped generating energy.

Additional Considerations: Running several tests can help you easily identify if the magnetron is giving you issues. Note: You can perform a magnetron’s resistance, but this is a dangerous process that is best performed by someone with a working knowledge.

How to fix: Fixing a broken magnetron is possible, but it can be a dangerous situation if you are unaware of the potential risks. Remember to take safety precautions. Additionally, a replacement magnetron can become costly, especially if you will seek professional installation.

1. Place a glass measuring cup with water into your microwave.
   • Room temperature water is recommended. 
   • Test the temperature of the water with a thermometer before and after 1 minute of it being in the microwave. 
   • Stir the water before taking the temperature after removing it from the microwave. Failure to do so can result in a bad reading.
2. Test your magnetron.
   • Remove the microwave plug from the outlet.
   • A suspended microwave will need to be removed.
   • Access the back panel and remove the screws. Do not touch any wires and wear rubber gloves for additional protection.
   • Locate the capacitor (a small box with a black cylinder sticking out)
   • Find the two metal prongs with wires running out of them.
   • Using an insulated screwdriver, grasp the insulated handle (do not touch any metal) and slide the metal part against the metal prongs.
   • Pay attention and listen for a snapping or clicking sound. This indicates you’ve successfully discharged the unit.
   • Remove the wire plugs and unscrew the magnetron.
   • Get a multimeter and ensure it is set on the lowest ohms setting.
   • Take the multimeter prongs and place them against the prongs on the magnetron.
   • Confirm if your reading is below or above 1 ohm. Anything higher than one (or OL) will mean the magnetron is faulty.

DO NOT

1. Attempt to test the magnetron without confirming you understand the process.
2. Attempt to remove the magnetron without 100% confirming the microwave is unplugged.
3. Attempt to discharge the capacitor without an insulated screwdriver.

DO

1. Maximize your safety with a pair of quality rubber gloves.
2. Ensure someone is around to help if an emergency does occur.
3. Consider the price and determine the most effective option.
4. Weigh your options. You can either order a replacement piece and install the new magnetron, or you might just want to replace the entire unit.

Additional Reasons

Metal in the microwave is one of the more common reasons an individual will experience a sparking microwave, but sometimes something more can be occurring behind the scenes. There are several other issues you might find helpful.

• Metal Base. This situation is similar to the concept of your microwave shelf becoming compromised and eroding. A common way to diagnose this issue is to view the plastic underneath. If it appears faded, it’s time to order your replacement piece.
• Stirrer. Your waveguide helps deliver the microwaves, but the stirrer ensures your unit is evenly distributing energy. A stirrer that is malfunctioning will generate an imbalance of energy and result in a microwave sparking. The best solution is to seek professional help as it can be easy to damage the entire microwave.

Read More: Frigidaire Microwave Not Heating: Causes and Fixes

Ways to Prevent Sparking

• Keep it clean. Don’t wait until the microwave starts sparking to scrub inside. Instead, wipe the microwave down with a damp rag after each use. This will help ensure less buildup over time.
• Cover your food. Take precautions to avoid food explosions inside your microwave. This will help limit the dirt and debris that can cause harm.
• Stability. Dropping a microwave can cause damage that contributes to a sparking problem. Always take measures to keep it protected.