Is Your Microwave Sparking? Here’s How to Fix It

It can be troubling to see your microwave sparking while it’s running, and you don’t want to leave this issue unresolved. Fortunately, there are some simple fixes for a sparking microwave that you can try, which we’ll cover in this guide today.

There are also some more severe issues, such as a faulty component, that can lead to sparking. It’s generally recommended to call in a professional to handle this as disassembling and fixing internal components yourself can be dangerous.

The microwave’s high-voltage capacitor holds a lethal charge even when the microwave is unplugged, so you must know how to discharge it first in order to perform internal microwave repairs safely.

Why is your microwave sparking?

Here’s why your microwave is sparking and how you can fix it.

There’s metal inside the microwave

If metal objects are accidentally placed inside the microwave, they can lead to sparking. Sometimes, a small piece of aluminum foil may find its way into the microwave and go undetected. Or perhaps the ceramic bowls you’ve been using have metallic decorations. Even small shards of metal from a steel wool scrubber can be enough to cause sparking.

It’s worth double-checking that there’s no metal inside the microwave or the containers you use. Give the microwave a quick clean with a damp, soapy cloth or sponge to be sure all flecks of metal have been removed.  

The microwave is dirty

A microwave left dirty for too long can eventually start sparking because food particles may overheat and ignite from absorbing excess microwave energy.

If a dirty microwave is the cause, the obvious solution is to clean it. Steam cleaning is an effective way to do that:

1. Fill a microwave-safe container with water and 1 tablespoon of white vinegar.
2. Place the container in the microwave and heat the solution for five minutes on the highest setting.
3. Let it sit for an additional few minutes to allow the acidic steam to work its magic.
4. Wipe the interior and turntable with a damp cloth or sponge to remove the loosened grease and grime.

The waveguide cover is damaged

The waveguide cover is a small rectangular panel normally found on the right side of the microwave interior. Its job is to protect the waveguide—which directs microwave energy into the cooking chamber—from food splatters, while still allowing the microwaves to pass through it.

The waveguide cover is often made of mica because this material is heat resistant and allows microwaves to pass through it. However, if the waveguide cover is damaged, such as it having burn marks or cracks, it can often cause sparking.

Replacing a damaged waveguide cover is an easy job you can do yourself. Here’s how:

1. Make sure the microwave is unplugged.
2. Remove the turntable.
3. Use a small flathead screwdriver to gently pry off the old waveguide cover, being careful not to chip the interior coating. If the cover is secured with screws, remove them with a screwdriver.
4. Clean the area revealed behind the waveguide cover with a damp, soapy cloth, and then dry the area.
5. Carefully install the new waveguide cover.

The interior coating is worn or chipped

The interior coating of a microwave helps prevent sparking, protects the metal walls from rust or corrosion, and makes the microwave interior easier to clean and maintain.

However, it’s possible for the interior coating to wear down, chip, or crack, which exposes the metal surface underneath, resulting in sparking when you run the microwave.

This often occurs because the microwave isn’t cleaned regularly, the coating was accidentally chipped by a sharp metal utensil, or harsh chemical cleaners or abrasive scrubbers were used inside.

Be aware, however, that not all microwaves have an interior coating. Some microwaves have an exposed metal interior, which is completely fine and normal.  

If, upon inspection, you notice that the protective coating—if your microwave has one—is damaged, follow these steps to fix it:

1. Unplug the microwave for safety.
2. Remove the turntable and any other items.
3. Clean the damaged areas of the interior coating with isopropyl alcohol to remove grease or debris.
4. Lightly sand the damaged areas, then wipe them clean.
5. Apply microwave-safe cavity paint with a small brush to the damaged areas.
6. Follow the paint’s drying instructions.
7. Apply one or two additional thin coats of cavity paint, depending on the instructions.

The diode is faulty

The diode helps the microwave produce the high voltage needed to power the magnetron. The magnetron is the component that generates the microwaves that heat your food. The diode powers the magnetron by converting alternating current (AC) into direct current (DC), which the magnetron requires to operate.

Over time, or due to power surges, the diode can fail. When this occurs, the microwave may still turn on but will no longer heat food and may start sparking.

Replacing a faulty diode is dangerous since it requires you to disassemble the microwave. We recommend you hire a professional to conduct this repair. However, if you’re confident you can handle it, here are the steps involved:

1. Unplug your microwave for safety.
2. Remove the microwave’s outer cover.
3. Discharge the high-voltage capacitor by using an insulated screwdriver to bridge the capacitor terminals. Do not skip this step!
4. Locate the diode, usually connected to the capacitor and magnetron.
5. Remove the screw securing the diode, and then disconnect it from the capacitor.
6. Test the diode with a multimeter if you’re unsure if it’s faulty.
7. Install the new diode by connecting it to the capacitor and securing it with the screw.

Problem solved?

If you’ve followed all of the steps outlined above and are still experiencing sparking in your microwave, we strongly recommend you stop using the appliance, unplug it, and call a professional to diagnose and repair the issue.

If your microwave is over seven years old and you prefer not to invest in repairs, it might be time to consider purchasing a new one.