6 Reasons Why Your Microwave Is Sparking

You go to reheat last night’s dinner for today’s lunch, when all of a sudden, there’s a flash of light and a loud sound coming from the microwave. You didn’t accidentally put the spoon in there, so why is your microwave sparking? There are a number of factors that can explain why your microwave is sparking; our guide will help you get to the root of the problem.

1. There’s Metal Inside the Microwave

We all learn as kids not to put silverware or other metal in the microwave, because it can spark. But even as adults, it’s easy to accidentally put metal or other non-microwavable materials in this appliance without realizing it. If your microwave is sparking, double-check that whatever container is inside is microwave-safe. Also, check that no bits of aluminum foil, steel wool, or other metal bits are stuck to the container.

2. The Mica Sheet Is Faulty

Inside the microwave is a piece of material called a mica sheet that looks similar to cardboard. The mica sheet, also known as a waveguide cover, shields the waveguide and other electrical components from food debris while still allowing the microwaves in the appliance to heat up your food. However, if the mica sheet is faulty, food debris can build up and burn, causing sparks. The mica sheet could also expose the metal components underneath it, which would also lead to sparking.

Savvy DIYers may be able to replace the mica sheet themselves. But because microwaves contain highly charged capacitors that pose shock or electrocution risks, it’s best to leave any part repairs or replacements to a pro.

3. The Microwave Interior or Racks Are Chipping

Some microwaves have racks that have a plastic coating to prevent the microwave from sparking. Microwaves also have protective coatings inside the heating area to protect the metal parts of the appliance. But if these coatings chip or crack, the metal will become exposed, causing sparks.

If the rack is chipping, you can order a replacement online. For the interior coating, there are touch-up paints made specifically for microwaves; however, these paints can be highly flammable, with vapors that may cause irritation to your eyes and respiratory system if you breathe them in. It’s best to leave these repairs to a pro. 

Better yet, consider saving up for the cost of new microwave installation, which is around $100 to $200.

4. The Diode Is Wearing Out

The diode is one of the most important parts of a microwave. This piece allows electrical current to flow in one direction from the power source to the magnetron, which creates microwaves. When the diode wears out or breaks, you may notice a burning smell, sparking, or that the microwave keeps tripping the breaker.

Don’t attempt to replace a diode yourself. The diode connects to the capacitor, which can hold dangerously high levels of voltage that pose a serious electrocution risk, even if the microwave is unplugged. You’ll need a pro to come discharge the capacitor before replacing the diode—or it may be time to buy a new microwave altogether.

5. The Door Switch Is Broken

A microwave has a door switch to stop the appliance from producing microwaves while the door is open. If the door switch breaks or becomes corroded, though, you may notice the microwave is sparking when it’s heating your food.

Replacing a faulty door switch requires handling wiring, so don’t attempt to DIY. Instead, hire someone who fixes microwaves, such as an appliance repair pro or electrician, for assistance.

6. The Magnetron Is Failing

In some cases, the magnetron may cause sparks in the microwave when it starts wearing out. More commonly, you’ll notice a loud humming from the microwave, or your food will still be cold after microwaving it.

As with other parts of the microwave, don’t attempt to inspect or replace a broken magnetron yourself. Leave microwave repairs, which cost around $100 to $200, to the pros.

What to Do If Your Microwave Is Sparking

Some causes of a sparking microwave, like accidentally putting a piece of metal inside the appliance, are easy to remedy. But if you can’t find the cause of the sparks, it may be time to consult a pro for repairs or replacement. Hire a local microwave installer to determine whether it’s an issue they can repair or if it’s time to upgrade your microwave to something safer.