The microwave has just one job: getting food hot fast. When the microwave has stopped heating—either not getting hot enough or not starting at all—you may be tempted to toss it out and buy a new one. It’s worth doing some troubleshooting, however, before giving up on the appliance. With a little time, a Phillips-head screwdriver, and a multimeter, you may be able to work through this list of common issues and get your microwave heating up again.
But first, some warnings: Unplug the microwave before you do any tinkering. If the plug isn’t accessible, turn off the power at the circuit breaker. Also, microwaves have a high-voltage capacitor, which stores electricity and forms part of the high-voltage circuit that powers the magnetron—the device that generates the microwaves that heat your food. The capacitor can deliver a dangerous shock, even after the microwave has been unplugged, and it must be discharged before doing any work on this circuit. If you are not experienced in electrical repairs, it’s better to call in a pro than to risk injury.
6 Possible Reasons Your Microwave Is Not Heating Up
1. Your microwave isn’t plugged in.
If nothing happens at all when you press the “start” button, make sure the appliance is plugged in and that the outlet has power. If it’s plugged in but not starting, check the breaker box to see if the circuit is tripped. If the breaker isn’t tripped, use a multimeter to test the outlet, or try plugging a lamp or another appliance into the outlet to see if it works.
2. The microwave has been set for a delayed start.
Some microwaves have a delayed start feature that lets the user program the appliance to start cooking at a set time. If this feature is selected, the microwave won’t immediately turn on when you press “start.” Check the user’s manual to find out how to cancel the setting. Alternatively, unplugging the microwave for a few minutes may reset the appliance and clear out the delayed start.
3. The control lock feature is turned on.
If nothing happens when you press the “start” button but the display is lit up, the control lock feature may be on. This feature prevents accidental use or use by children. When it’s on, there is usually an indication in the display. Control lock can often be canceled by holding down the “cancel” or “off” button for a few seconds or by repeatedly pressing it, but check the user’s manual for your microwave. On most but not all models, unplugging the microwave for a few minutes will cancel the control lock setting.
4. The microwave may be in demo mode.
If the appliance is on, the display is lit up, the microwave fan is running, and the turntable is spinning, but the microwave will not heat up, the appliance might be in demo mode. Retailers use this setting to demonstrate the appliance’s features without using actual microwave power. The process for turning it off varies from model to model, so check the user’s manual for instructions or simply unplug the microwave for a few minutes to reset it.
5. Your microwave is set to a low power level.
If the microwave no longer heats up food properly or heats very slowly, check the power setting. Microwaves typically offer between five and 10 different power levels for more precise cooking, making the appliance effective at everything from softening butter to cooking stews to heating a cup of water for tea. Check the power setting to make sure it’s appropriate for the food you’re heating.
6. One of the door switches is bad.
Switches on the microwave’s door—typically three, but sometimes more—prevent the appliance from operating with the door open. This is an important safety feature, but sometimes a faulty switch can prevent the microwave from heating up, although the light and turntable may go on, and the timer may count down. A bad switch can also cause the fan and turntable to run when the door is open.
These switches are located on the inside of the microwave door by the latch mechanism. Accessing the switches typically requires removing some of the appliance’s exterior trim and the control panel. The process varies by model, so check the user’s manual or look for instructions online. Take photos before and while you’re removing the switches to make sure you reinstall them properly.
Use a multimeter (see our collection of the best multimeters) to check each switch for continuity, confirming that power flows through when the switch is closed. If the multimeter reads close to zero when the switch is closed, the switch has continuity. If not, the switch needs to be replaced.
When to Call a Professional for Microwave Repairs
While there are a number of other components that can be checked or replaced, the U.S. Consumer Product Safety Commission and major manufacturers strongly discourage DIY microwave repairs. For homeowners who do have the appropriate skills and experience, here are some other potential problem points worth checking if the microwave is running but not heating. Working with any of these components requires that you first discharge the high-voltage capacitor using a rubber-handled screwdriver or other safety tool.
The high-voltage diode has failed.
The diode is the piece of equipment that converts alternating current (AC) into direct current (DC), providing power to the magnetron. If it’s burned out, the magnetron will not receive enough voltage to generate the microwaves that heat the food.
The high-voltage capacitor is faulty.
The capacitor stores electrical energy and discharges it to the magnetron, ensuring that it receives the roughly 4,000 volts needed to generate microwaves. If the capacitor is faulty, the oven won’t heat up, and it may make strange humming, buzzing or crackling noises.
The magnetron has failed.
The magnetron generates the microwaves that heat the food. When a magnetron fails, it can also blow fuses, which can cause other failures in the microwave.
It’s recommended that a faulty magnetron be replaced by a professional due to the dangerous nature of high-voltage repairs. The magnetron is relatively expensive to replace, so it may be worth replacing the microwave if the magnetron has gone out, especially if it’s an older unit.
When Should You Replace Your Microwave?
If after troubleshooting the appliance you’re still wondering why your microwave isn’t heating, it may be time to buy a replacement. The lifespan of a microwave is about 7 years, depending on the quality of the appliance and how often you use it. It generally doesn’t make sense to repair a microwave that’s more than 7 years old. Instead, look at new models that may be more energy-efficient or offer useful features like convection cooking.
It is often, however, worthwhile to repair a microwave, even an inexpensive one, if it’s less than 3 years old. To decide whether to replace a broken microwave older than 3 years, consider the initial cost of the microwave and weigh that against the cost of the repair and the cost of a new model with the desired features. If you’re replacing an over-the-range microwave, be sure to factor in the cost of installation as well as any cabinet or venting modifications the new unit may require.
Dispose of your microwave responsibly if you do decide to buy a new one. Check with your local sanitation department to find out if the appliance needs to be taken to a special collection site for recycling or proper disposal. If the old unit is still in working condition, consider donating it; if it needs some work, ask a local appliance repair shop if they’re interested. Do what you can to keep the microwave out of the landfill.
Maintain Your Microwave to Make It Last
To extend the life of your microwave, avoid making these common appliance mistakes.
- Don’t use the microwave for certain foods, such as eggs in the shell, which can explode; grapes, which can spark; and sealed containers of food, which can explode.
- Don’t put certain items in your microwave, including styrofoam, twist ties, paper bags, foil, and other metals.
- Clean the microwave frequently to prevent odors and keep the appliance running efficiently. Food buildup can lead to poor performance and even fires.
- Don’t run the microwave when it’s empty. Running an empty microwave for too long can cause the appliance to overheat and even lead to fires.
- For over-the-range microwaves, use the exhaust fan when you cook and clean the filter regularly to protect the microwave’s components from damage.
- Don’t slam the microwave door. Rough treatment can damage the latch mechanism and switches.
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