Microwave Sparking? (here’s what you need to know)

If you notice sparks when heating up food in your microwave it can be worrying. As we all know, sparks can lead to fires and no one wants a fire breaking out in their microwave.

There are several reasons why your microwave might start sparking from a simple case of pieces of old food debris to something as serious as a defective magnetron.

In this article I take a close look at the causes and solutions of sparks in the microwave. Keep reading to find out more.

Please Note: Some of the components of a microwave can store enough electricity to cause serious injury or even death for up to 48 hours after the appliance has been disconnected from the power supply. Which is why I recommend contacting a technician to investigate and replace any parts that require the dismantling of the microwave’s cabinet to access.

Why Is The Microwave Sparking?

There are a number of reasons why your microwave might be sparking when heating up food. They include;

Probable CauseSolution
Food Placed Too Close To The Body Of The ApplianceRearrange the food ensuring it isn’t too close to the body of the microwave
The Remains Of Old Food Starting To BurnEnsure the microwave is clean and no old food debris remains
Using Metallic CookwareEnsure all containers etc used in the microwave are microwave safe
Defective/Damaged Waveguide CoverReplace the damaged waveguide cover
Defective Or Damaged FanInspect and replace the fan if necessary
Electrical ProblemsContact a technician
Faulty High Voltage DiodeContact a technician
Defective MagnetronContact a technician

Let’s take a closer look at each of these issues;

Food Placed Too Close To The Body Of The Appliance

person placing a bowl of food inside a microwave

If food items are placed too close to the body of the microwave, it can cause sparking. To prevent this from happening always ensure the food is placed as close to the centre of the plate as possible.

Never allow food to touch the sides of the cabinet to prevent sparking or the outbreak of fires.

The Remains Of Old Food Starting To Burn

If there has been some spillage in the past and you’ve failed to clean it all away, it could lead to sparks flying in the microwave. What happens is these burnt food particles become superheated when the microwave is running.

This leads to them creating sparks which could potentially cause a fire. To prevent this from becoming a problem, always ensure the interior of the microwave cavity is clean and free from any food or other debris.

Using Metallic Cookware

potatoes on aluminum foil

It is incredibly dangerous to use any metallic cookware in a microwave. This includes ceramic plates with a metallic trim, takeaway containers made from aluminium foil, cardboard containers with metal fasteners or anything else which doesn’t carry the microwave safe symbol of three wavy lines or the words “microwave safe”.

When metal of any kind is placed in a microwave, it can cause sparking and then damage to the microwave’s components. To prevent this from happening you should never use any metal cookware or anything with metallic trim or fasteners etc in the microwave.

This includes aluminium foil containers or coverings which can easily lead to fires breaking out in the microwave.

Defective/Damaged Waveguide Cover

The waveguide transfers power from the magnetron to the cooking chamber. The waveguide is covered by a waveguide cover which is typically made from a rectangular piece of silver card. Which allows the rays from the microwave to heat up the food or drink in the appliance.

If the waveguide cover becomes dirty from grease, or food particles, it can lead to sparking inside the microwave. This can be a common problem in older, well used microwaves.

You need to check the waveguide cover for any dirt, grease or food particles and remove them using warm soapy water. If the waveguide cover is damaged however, it will need to be replaced.

Defective Or Damaged Fan

Inside the microwave there is a fan (often called the stirrer fan) which distributes the microwave energy evenly through the cooking chamber. If this fan is damaged or defective, it won’t work properly and can cause sparking.

You can locate and inspect the fan yourself or contact a technician to do it for you. If the fan is dirty or obstructed, you should clean it and remove the obstruction using a soft cloth. However, if the fan appears to be damaged, it will need replacing.

Electrical Problems


There are various wires, circuits and components inside a microwave that could all experience problems leading to sparking. This is particularly common in older appliances or those that have been subjected to a lot of use.

As inspecting all of the wires etc in a microwave involves dismantling the cabinetry, I recommend contacting a technician to inspect and repair any shorted, burnt out or damaged wires or components.

Faulty High Voltage Diode

The high voltage diode directs power from the capacitor to the magnetron. If the diode has developed a fault, it could cause sparking.

As inspecting and testing the diode involves dismantling parts of the microwave, I recommend contacting a technician to do this for you.

Defective Magnetron

The magnetron generates the microwaves used to heat the food and drink in your microwave. If it develops a fault or becomes damaged, the magnetron can cause sparking.

This typically occurs in older, more well used appliances. If the magnetron is defective, you may hear a loud buzzing sound and/or smell burning when the microwave is running.

If you suspect the magnetron is the reason your microwave is sparking, I recommend contacting a technician to investigate further. It often works out financially more viable to buy a new microwave rather than replacing the magnetron on your old model.

SEE ALSO: Air Fryer Vs Microwave: What’s better & cheaper?

Frequently Asked Questions

Why is my microwave sparking and popping?

If your microwave is sparking and popping it is often caused by food items with a high fat content as they cook. You can reduce these sounds and help prevent the sparking by covering the container the food is cooking in with a vented lid.

Is it bad if your microwave sparks?

Yes, it is bad if your microwave sparks because the sparks could lead to a fire and it’s not normal for a microwave to spark. It could be caused by a number of things including; Food items placed too close to the body of the cooking chamber, old food particles stuck on the interior walls of the cooking chamber, something metallic in the cooking chamber, a defective waveguide cover, a damaged or defective fan, a defective high voltage diode, electrical issues or a defective magnetron.

Is it safe to use a microwave that sparks?

No, it is not safe to use a microwave that sparks. Stop the microwave immediately and check that you haven’t used any metallic cookware. Then check that the cooking chamber is clean and free from any food particles and that the food has been placed as close to the centre of the cooking chamber as possible. If the sparking has not been caused by any of these reasons, you need to get the microwave checked out professionally before using it again.

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