Top Causes of Microwave Malfunctions

By Lyle Weischwill | Dec. 27, 2023 1:44 pm PST

Homeowner having a microwave malfunction.

Microwaves are convenient kitchen appliances, but like any other electronic devices, they can experience various failures. There are many reasons why your microwave won’t work right.

Whether the light won’t turn on, the fan doesn’t work, the microwave won’t heat or the turntable won’t spin, finding the cause of a microwave failure will help you decide whether you can fix the problem yourself, have a professional repair the failure or replace the microwave.

Here are common causes and safe resolutions for microwave malfunctions.

Microwave Won’t Turn On

When the microwave has no power at all, start by making sure that its power cord is plugged in. Next, make sure the electrical outlet is working. Plug a small lamp or appliance into the electrical outlet. If the outlet has no power, reset the house circuit breaker for the outlet. If the outlet is still dead, you’ll need to have an electrician fix the electrical outlet.

If the electrical outlet is okay and power cord is plugged in securely, a failed electronic control board or internal wire failure could be preventing the microwave from powering up. A service technician will need to diagnose and repair these types of failures. You may also consider replacing the microwave when it won’t work at all.

Image of homeowner attempting to start a broken microwave oven

Microwave Won’t Start

When the microwave won’t start, one of these failures could be causing the problem.

  • Broken door switch. The microwave won’t start unless the control detects that the door is fully shut. A bad door switch won’t accurately detect that the door is closed. A technician will need to replace a bad door switch or you’ll need to replace the microwave when it won’t start due to a bad door switch.
  • Blown internal fuse. Internal fuses blow when an electrical short occurs or when the microwave overheats. A service technician will need to diagnose and repair the microwave when an internal fuse blows. Replacing the microwave is another option you can consider.
  • Faulty magnetron. The magnetron produces the high-energy waves that heat the food in the microwave. Check the owner’s manual for your microwave when you suspect a magnetron failure. The magnetron in some microwaves has a 10 year part warranty but you have to pay for labor to replace the magnetron. You may consider having the microwave repaired when the magnetron fails and the part is under warranty. If the magnetron isn’t under warranty, you’ll likely need to replace the microwave.
  • Bad diode or high-voltage capacitor. The microwave components need to be replaced by a technician when they fail. You may also consider replacing the microwave instead of repairing it.
  • Defective electronic control board. A bad control board can prevent the microwave from heating. A technician would need to test the control board output and repair the microwave if it has a defective control board. Replacing the microwave is another option when the appliance has this failure.

Microwave Won’t Heat

The same failures listed above except for a broken door switch will prevent the microwave from heating while it runs. A technician will need to diagnose and repair the problem or you can replace the microwave when it won’t heat.

Arc Marks Inside the Microwave

If you notice sparks inside your microwave while it’s running, it could be because foil or utensils are inside, or the interior paint could be chipped, exposing the metal of the microwave. If there are spatters of food inside your microwave, they could be continuing to cook when you turn it on, which can also cause sparks. Clean the internal cavity of your microwave thoroughly.

You can repair some types of arc marks and burns using touch-up paint.

This video will walk you through that process and show you some ways that you can avoid burning your microwave in the future.

For microwaves that are not stainless steel on the inside, you can repair arc marks up to the size of a quarter using this touch-up paint, but only if the marks appear on the inside walls, the floor, or the ceiling. Don’t attempt repairs on the outer frame, or the door. Any repairs to the door or frame could affect the shielding and cause radiation leaks. And don’t attempt repairs on burn marks larger than a quarter, as that could be a sign of a more serious problem and should be checked out by a service technician. Also, don’t use this repair on microwaves with a stainless steel the inside, because the paint won’t stick.

If you’re unable to repair arc marks or burns inside the cavity, schedule service by a technician or replace the microwave.

Microwave Light Won’t Work

A burnt out light bulb often prevents the internal light or cooktop light from working in your microwave. Check the owner’s manual for your model to see if you can replace the light bulb yourself. Follow the instructions in the manual to replace the light if you find that procedure covered.

In many microwaves, the internal light needs to be replaced or fixed by a service technician. Schedule service or continue to use the microwave without the internal light. You can also replace the microwave when the internal light quits working and you’re unable to safely fix the problem yourself.

If replacing the light bulb doesn’t fix the problem, a wiring failure, bad light socket or defective control could be preventing the light from working. Have the microwave repaired or replace it unless you can do without the light.

Turntable Not Moving

When the turntable in your microwave isn’t rotating, first check that it’s properly aligned on the turning mechanism. It can easily become loose and fail to turn properly. Aligning the turntable properly may fix the problem.

Next, check the settings to make sure turntable rotation is selected. Adjust the turntable setting if necessary.

If the above troubleshooting tips don’t help, then a bad turntable motor or a wiring failure could be preventing the tray from rotating. You’ll need to have a service technician diagnose the problem and fix the microwave when the turntable won’t move. You can also replace the microwave.

Touchpad Not Working

When the touchpad isn’t working, try unplugging the microwave power cord for 3 minutes to reset the electronic control board. Plug the microwave back in to restore electrical power. The touchpad may work normally. If not, you’ll need to have the microwave repaired because the control board or touchpad will likely need replacing. You can also replace the microwave instead of repairing it.

Don’t attempt microwave repairs that aren’t covered in the owner’s manual. Microwaves have a high-voltage capacitor that retains a lethal electrical charge even when the microwave power cord is unplugged. Also, a service technician needs to test the microwave for radiation leakage following any disassembly or repair. Don’t risk your health and safety by attempting DIY microwave repairs.

Schedule microwave service through Sears Home Services when your microwave needs repair.

Because microwaves are inexpensive appliances, it’s often less expensive to replace the unit rather than repairing it. We can help you with that, too.

Image of the Sears upgrade webpage

To seamlessly replace your microwave (and other appliances if needed), visit our Upgrade page to conveniently select a new appliance or appliances and get help with special financing.

We’ve consolidated all help, financing offers and savings into one location on our Upgrade page to make it easy for you to replace your appliances now. No hassles and no waiting.

Sears carries a wide selection of microwaves and other appliances from top brands like Kenmore, GE, Samsung and LG. Get your new home appliances right away.

Sears Home Services is here to help you manage your home easier whether it involves troubleshooting, repair or appliance replacement. Trust us to help you take care of everything in your house so you can truly enjoy your home.

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