BACKFEB 21, 2026
Seeing sparks inside your microwave—often called "arcing"—is one of the most alarming things that can happen in a kitchen. It looks dangerous, sounds loud, and can make you worry that the appliance is about to catch fire or explode.
Looking for more guidance? Take a look at our Repairs overview.
Take a deep breath. While you definitely shouldn't ignore it, a sparking microwave doesn't necessarily mean the unit is trash. In fact, the cause is often something simple that you can fix yourself in just a few minutes.
This guide will walk you through a safe, step-by-step process to identify why your microwave is acting up and how to stop it.
Sparking occurs when high-voltage microwave energy can't be absorbed by the food and instead jumps between conductive surfaces. This usually happens for one of three reasons:
Let's figure out which one is affecting your kitchen.
![Microwave sparking]
Safety is the priority here. We are dealing with electricity, so follow the order of these steps carefully.
Before you stick your hands inside or inspect anything closely, make sure the appliance is safe to handle.
The most common reason for sparking is simply user error. We've all been there—leaving a spoon in a bowl or not realizing a takeout container has a metal handle.
If there is no metal inside, the culprit is likely the walls of the microwave itself. Old food splatters that have been cooked over and over eventually turn into carbon. Carbon conducts electricity, which leads to arcing.
How to Deep Clean:
Test: Once everything is dry and reassembled, run the water test again (30 seconds on high). If the sparks are gone, it was just a dirty microwave. Keeping a cleaning schedule in an app like Casa can help prevent this buildup from returning.
If the microwave is clean and metal-free but still sparking, look at the waveguide cover. This is a small square or rectangular panel, usually located on the right side wall or ceiling of the interior. It looks like cardboard or mica plastic.
Its job is to protect the magnetron (the part that makes the heat) from food splatters.
How to Replace:
Test: Run the water test again. If this was the issue, the sparking should stop immediately.
The interior of your microwave is actually made of metal, but it's coated in a special paint that prevents the microwaves from reacting with it. If that paint chips or peels, the exposed metal can cause arcing.
How to Fix:
Test: After the paint cures, run the water test.
If you have removed all metal, cleaned the interior, replaced the waveguide cover, touched up the paint, and the unit still sparks, you likely have an internal electrical failure (such as a failing magnetron or high-voltage diode).
At this point, stop using the microwave immediately. Internal electrical repairs on microwaves can be dangerous due to high-voltage capacitors that hold a charge even when unplugged. It is time to call a pro or replace the unit.
Fixing a sparking microwave is usually very affordable compared to buying a new one.
Most of the time, a sparking microwave looks much worse than it actually is. By methodically checking for metal, cleaning up old spills, and inspecting the waveguide cover, you can often save the appliance and avoid the cost of a replacement.
Once you’ve got your kitchen back in order, it helps to keep track of maintenance so you aren’t caught off guard again. The Casa app is great for organizing your home’s appliance details and manuals, so if you ever need that specific part number for a waveguide cover again, it’s right at your fingertips.
Ready to feel more in control of your home repairs? Download the Casa app today.
