Microwave Sparking? 5 Common Causes and How to Fix It

A sparking microwave is a symptom that needs immediate attention and care. Whether the parks are contained within the oven compartment or appear around the exterior of the microwave you should act fast and switch off the power to prevent an accidental shock or potential fire hazard. In this article, I’ll cover the most common reasons for microwave sparking and what you can do to fix it.

High Voltage Discharge

Microwave ovens are high-voltage appliances and as such need to be treated with respect. The remedial action provided in the list below is split into two categories. Those suitable for general repair by any appliance owner, and those reserved for a professional technician.

If your microwave is sparking this will most likely be the result of a high-voltage reaction. If an internal inspection is required, where the outer casing needs to be removed, then this process is best left to a professional. Microwave ovens store electricity, by design. Unplugging the appliance will not necessarily make the microwave safe to inspect until the capacitor has been appropriately discharged.

How To Discharge Electricity In Microwave:

1. Unplug the microwave from the mains electricity
2. Carefully remove the out casing to expose the internal components
3. Take a well-insulated screwdriver and touch the tip of the screwdriver onto a terminal
4. Slide the screwdriver across the chassis of the microwave to the opposite terminal
5. Hols the screwdriver on the second terminal until you hear a very distinctive cracking noise. This noise is the electricity discharging
6. Do this for each terminal

5 Reasons Your Microwave is Sparking

If you see sparks when using your microwave you would be right to be concerned. It could be caused by something as innocuous as a metallic object accidentally being placed inside the microwave oven or something much worse such as a fault in the electric circuitry.

To help you resolve this worrying situation, I have listed the 5 most common reasons why a microwave oven would create flying sparks. Each is listed in order of the most probable cause, with number one being the most probable. Work through each option in sequence, and this will help you troubleshoot your problem in the most efficient way possible.

1. Metal Object In Microwave

One of the most common problems that we see is customers accidentally placing a metallic object in the microwave during heating. It’s an easy mistake to make. Nine times out of ten the sparks are produced by takeout carton lids or a fragment of aluminum foil attached to a container or food. But there are other less obvious triggers to look out for, such as tableware with decorative designs that contain a metallic paint finish, often around the rim of the cup or plate. Or perhaps the user has cleaned the inside of the microwave with wire wool or a metal scouring pad and tiny fragments of metal remained within the oven housing, after cleaning.

Items To Look Out For:

1. Tableware or cups with metallic decorative rim
2. Small fragments of steel wool, left over from cleaning
3. Metal cutlery was accidentally left in the container after stirring
4. Takeout carton lids with a metallic underside
5. Fragments of kitchen aluminum foil left on food being reheated

If you notice a spark or a crackling noise within your microwave oven, you should immediately disconnect it from its power source to prevent additional damage or a potential fire. Check the contents of the microwave for any metal object. If you cannot see any obvious cause, remove the rotating plate and look for fragments of wire wool or similar substances. Once you are satisfied the oven area is clear of any metal objects, I suggest trying the microwave again, but without any contents. This will confirm the area is clear. If you then choose to continue with your original task of reheating food and the microwave sparks again, you can be sure the problem is being caused by your food container.

2. Worn Microwave Racks

Does your microwave have racks? If so, it’s possible they are generating sparks. Microwave racks are usually made from metal that’s coated in protective plastic material. But over time with regular use, the plastic coating can wear, crack or peel, resulting in the rack’s metal frame becoming exposed. Take out the racks and give them a thorough visual inspection, look for any signs of the plastic coating being cracked or worn.

Whilst the racks are outside of the microwave, turn the microwave on and check for any further signs of sparks. If you see no more sparks whilst the racks are outside of the microwave, you can be pretty certain they were the problem. You can now simply purchase a new set of racks.

3. Damaged Waveguide Cover

The waveguide cover directs microwaves toward your food to heat it through. It also plays a secondary role in protecting the magnetron from debris and food splatters. If you’re not familiar with what the waveguide cover looks like, it’s a fairly unimpressive rectangular sheet of coated metal. It looks a little bit like the underside of a takeaway carton lid and it’s located on the inside wall of the oven case.

This component can get damaged easily, corrode or wear over time as it’s thin and not very robust. Take a look at it, and inspect it for signs of damage or corrosion on its surface. If you spot any sign of wear and tear it’s best to order a replacement part to avoid any doubt, as they are inexpensive and easy to replace. You can pick them up here at Amazon.com for under $10.

Replacing the waveguide cover is as simple as unscrewing the old one and screwing in the new one. However, make sure that your microwave oven is unplugged when you’re replacing the component.

4. Faulty Diode

If you see sparks flying and notice a burning smell coming from your microwave, it may be due to a faulty diode. When the diode is not working properly, it will also prevent your microwave from heating food.

How to Replace a Faulty Diode

You can find the diode underneath the bottom panel of your microwave. All you need to do to replace it is remove the screw securing the component and put an adequate replacement in its place.

Here’s a short video on how to replace it.

Microwave Isn't Heating? Diode Replacement #W10492278

5. Faulty Magnetron

The magnetron is one of the most important components inside a microwave oven. Its function is to produce the microwave energy that heats your food. Like any other component, the magnetron can fail and stop working with general wear over time. If you have checked all other probable causes I have listed in numbers 1 to 4, you should test the magnetron for electrical continuity.

How to Test a Faulty Magnetron

Testing a faulty magnetron is a simple process for a competent technician, that only takes a few minutes. Here’s how to do it.

1. The first step is to remove the casing from each side of the microwave and locate the magnetron. It will look like two metal boxes, stacked one on top of another.
2. Unscrew the magnetron with a screwdriver and pull it out of the appliance gently.
3. Now take your multimeter and make sure that it’s on the lowest ohm setting.
4. Connect the multimeter’s leads to the terminals of the magnetron and check whether you get a reading below 1 ohm. If you do, then your magnetron is working properly. However, you should do one further test.
5. Now grab the multimeter and set it to the highest ohm setting. Take one of the leads and place it against the magnetron’s metal casing. Take the other lead and place it on the metal box.
6. If you get a reading that shows “OL” or “Open Line”, the component is working.

If you’d like to see how to replace a faulty magnetron, you should check out the video below.

Checking and Replacing Magnetron in a Microwave. ( Runs but no heat )

Microwave Sparking From The Outside

If the sparks of electricity are coming from the outside of your microwave, perhaps near the power cord or maybe from the underside of the microwave case, take extreme care. The most likely cause of this type of spark is a breakdown of the electrical insulation of a component or the wiring. If you consider the charge creating this spark is most likely from the main power outlet, then you can appreciate the risk of a high voltage shock, with potentially fatal consequences.

How to Fix

The first thing you’ll need to do is immediately unplug the microwave. I am going to keep this part very simple. DO NOT attempt to repair this type of electrical fault. Either call in a professional appliance technician or consider purchasing a new microwave oven.

Microwave Sparking After Cleaning

It often happens that people notice microwave sparking after they clean the appliance. In nearly all cases, this is due to a small piece of metal is left behind. Many people use steel wool to clean appliances. If even a tiny piece of it is unintentionally left in your microwave, it can cause sparks to fly.

How to Fix

The first thing that you need to do is unplug your microwave and wait at least half an hour for it to discharge. After that, thoroughly inspect the microwave for any metal pieces and remove them.

Is A Sparking Microwave Dangerous

Microwave sparking is a scary sight, but is it also dangerous? If you’ve noticed sparks starting to fly in your microwave, you should instantly turn them off. As long as the sparks are inside the microwave, they won’t harm you. Nevertheless, they will likely damage your microwave oven. In case you notice sparks coming from the outside, it can be dangerous. Unplug the microwave as soon as possible and stay away from it for a few hours to allow it to discharge.