by Kimz


Last Updated on

Are you having problems with your microwave oven? Does it seem like it isn’t heating up at all? If so, you are not alone. Many people have experienced this issue when trying to cook a quick meal or heat up their leftovers. Thankfully, there are some simple steps you can take to troubleshoot the problem and figure out what could potentially be wrong with your appliance. Keep reading to find out how!

It is no secret that many of us rely heavily on our microwaves for cooking and reheating food in just a few minutes. But what happens when the oven doesn’t seem to be working properly anymore? It may seem intimidating, but there are several common causes behind why a microwave oven may not be heating up, and you’ll be glad to know that it is fairly easy to troubleshoot the issue. Let’s take a look at how microwaves work, as well as some of the things you should check if your microwave isn’t working properly.

How Does Microwave Oven Work?

A microwave oven works by using high-frequency radio waves to rapidly heat food. The waves are generated by a component inside called the magnetron. Inside the cooking chamber, these radio waves cause particles in food molecules to move around at a rate of millions of times per second; this rapid movement causes friction between molecules and generates heat.

How to repair a microwave that is not heating:

Once you have determined that your microwave is not working, there are several components you should check to see if any of them require replacement.

High-Voltage Diode:

When a microwave is not heating up, the high-voltage diode may be at fault. This part acts as a safety device that keeps the power supply in check, and if it malfunctions, it can result in your oven not heating properly. To replace this diode, you will need a few supplies including an Ohm meter and some specialized tools for disassembling your appliance.

First, disconnect the power cord from the wall outlet and remove any food items or packaging from inside the microwave oven. Secondly, use your Ohm meter to check the low resistance of each lead of the capacitor–if one side has no reading or reads lower than usual, the high voltage diode is likely defective.

Thermal Fuse / Thermal Protector:

This safety device helps protect the oven from overheating and short-circuiting. If it has blown or become damaged in some way, then it will cut off power to the magnetron so that it won’t heat up anymore.

High Voltage Capacitor / Transformer:

The capacitor and transformer are responsible for supplying the necessary power to the magnetron. If either of these parts has gone bad, then it could be preventing the oven from heating up properly.

A malfunctioning high-voltage capacitor can be the culprit behind a non-functional or underperforming microwave oven. To verify the issue, locate and unscrew the panel from the bottom of your microwave oven and then check for any signs of damage or burnt spots on the capacitor. Once identified, it is best advised to replace the component with a new one.

Control Board:

The control board is a computer that regulates several different functions of the microwave, including when and how much power is sent to the magnetron. If this part has gone bad or become damaged in some way, then it can prevent the oven from heating up properly.


This is the component that generates radio waves that heat up food. If it has gone bad or burned out, then it won’t be able to generate any heat and the oven won’t heat up.

Door Switch:

This is a small switch inside the microwave door that detects when it is open or closed. If this switch has gone bad, then it can prevent the oven from heating up properly.

The first step is to open the access panel on your microwave oven and locate the door switch near the door hooks. It should be a black button located at the edge of the door frame; when you close the door, it should press against this switch. You can then use a multimeter to test if the signal is being sent from the switch when it’s pressed down. If there’s no signal or only an intermittent one, then it’s likely that you need to replace the door switch altogether.

Once you’ve identified that you need to replace the door switches, you can disconnect them from the wiring and pop in a new one. Make sure to get a compatible replacement by looking up your microwave’s model number or double-checking with an appliance technician. When installing the new switch, make sure it is secured tightly and that no wires are frayed or exposed.

Finally, reattach the access panel and give your oven a test run! With any luck, your dinner guests will be enjoying perfectly cooked food before too long.

How to determine if a component has failed or a fuse has blown:

To determine if the microwave components have failed or if a fuse has blown, you will need to use a multimeter to measure the electrical resistance between individual parts. The readings should tell you which components have gone bad and need to be replaced.


If your microwave oven isn’t heating up, don’t worry! There are several common causes behind why it might be having trouble, and thankfully they are fairly easy to troubleshoot. Make sure you check all the components outlined above—especially the high-voltage diode, thermal fuse, high-voltage capacitor/transformer, control board, burned-out magnetron, and door switch—to see if any of them need to be replaced. With a little bit of patience and some basic troubleshooting skills, you should be able to get to microwave repair and keep your microwave up and running in no time! Good luck!

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