Is Your Microwave Not Heating? Here Are 7 Most Common Causes

Posted By On 03-08-2022

If you've ever had your microwave stop heating, you know how frustrating it can be. There are a few possible reasons why your microwave might not heat up food properly. It could be a problem with the power supply, the magnetron, or the door seal. If you're having trouble with your microwave, check out these three possible causes. But first, let's look at how a microwave that works properly warms up food. 

An Overview of How Microwave Ovens Work 

Microwave ovens are definitely meant for convenience in the kitchen. They're perfect for heating leftovers or quickly preparing a meal. But how do they work?

Microwave ovens use electromagnetic waves to heat food. These waves are produced by a magnetron located inside the oven. The waves bounce around inside the oven and are absorbed by the food, which makes it hot.

If there’s something wrong with your microwave, it may be a lot tougher to fix it yourself. Unlike a standard oven, it’s not just a heating component that you have to repair. 

Here are the seven most typical causes of your microwave that’s not heating:

 1. The Magnetron is Broken 

A broken magnetron is one of the most common reasons your microwave might not heat up. The microwaves that heat your food are created by the magnetron. If it's broken, the microwaves can't be generated, and your food won't get heated.

 2. The Diode is Broken 

Another common reason for microwaving and not heating is the broken diode. The diode is responsible for controlling the flow of electricity to the magnetron. If it's broken, then the electricity can't flow properly, and the magnetron won't be able to do its job.

 3. The Microwave Is Overloaded 

If your microwave is overloaded, then it may not be able to generate enough heat to actually cook your food. This is usually because there's too much food in the microwave or because the food is too dense. Either way, if your microwave is overloaded, then it probably won't be able to heat your food properly.

 4. The Waveguide is Blocked 

If your microwave isn't heating, it could be because the waveguide is blocked. The waveguide is a metal shield that covers the microwave cavity and controls the path of the microwaves. If it's blocked, the microwaves can't reach your food, and it won't get hot.

To clean the waveguide, remove it from the microwave and wipe it down with a damp cloth. Before replacing it, you should ensure it has been properly dried out. If the waveguide is damaged, you'll need to replace it.

 5. Faulty Door Seal 

Another possible cause of a microwave, not heating is a faulty door seal. If the seal around the door is damaged, it can allow microwaves to escape, making it difficult for the oven to heat food properly. Finally, a defective heating element can also prevent the microwave from heating food properly. If the element is burned out or damaged, it must be replaced.

6. The Door Switches May Be Defective

A majority of microwave ovens have three or four door switches that let the microwave start or heat up when the door is shut. If the door switch is broken, even if the door is closed and locked, the microwave won't heat up. You can use a multimeter to check the electrical continuity of each door switch, just like you did with the diode, to see if one or more of them have failed.

 7. It Has a Faulty High Voltage Capacitor 

Since the capacitor works with the diode to convert and double the current going to the magnetron, a bad capacitor will stop the whole high voltage circuit from working. When a capacitor goes bad, it tends to bulge or leak. Even if there aren't any obvious signs of failure, you can test the capacitor with an analog Ohm meter or a capacitor tester.

See if it can store and release its charge and has an acceptable capacitance rating. Make sure the capacitor is empty before you touch it.


When your appliances break down, they can interrupt your productivity, whether you use the microwave at home or for your business. Faulty microwaves cause continuity errors that can be damaging for any business. So don't ignore getting your microwave fixed as soon as you find it faulty.

Do you need a professional appliance technician in Toronto? Pro Appliance is a reputable home appliance service and repair company that offers reasonable rates. Call us today to find out more!

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