Microwave Turns On But Does Not Heat: What Seems to be The Problem?

In most households, a microwave is perhaps one of the staples when it comes to appliances. It can be a handy tool, especially when it comes to reheating food. However, there are instances wherein different problems are experienced. This can be frustrating, especially when you seem to be clueless on how to have it solved.

Among others, one of the most common problems is that microwave turns on but does not heat. Before you finally jump to a conclusion that you need a new microwave, keep on reading and learn about some of the possible issues.

Problem with the Power Diode

One of the first things that you should look at is the power diode. This is one of the most important electronic components of the microwave. A diode will function as a single-way switch where current will flow through. Once it becomes problematic, the microwave will not produce heat and oftentimes, this will be accompanied by a hissing sound.

However, it should be noted that replacing a defective power diode is not an easy task, especially for someone who does not have knowledge in electronics. With this, it is better to rely on the help of experts to be sure that the problem will be solved instead of getting worse!

Problem with the High Voltage Capacitor

The high voltage capacitor in the microwave will work hand-in-hand with power diode for the conversion of electricity. There are instances wherein it will end up being burnt. In such instance, it will not work. This will also create an audible sound and will not cause the microwave to heat.

Determining if the high voltage capacitor is the problem will not be easy, at least for most of us. A skilled technician with a VOM meter will be needed. Through capacitance testing, it will be easy to determine if this is indeed the problem.

It should be noted that the capacitor holds power like a battery. Even if the microwave is unplugged, it can release electricity that could even lead to death in serious cases. With this, make sure that the capacitor will only be handled by a pro.

Problem with the Magnetron

This is another electrical component that can seem to be the problem when the microwave turns on but does not heat. It generates the frequency that is needed by the microwave to produce heat and cook food. Therefore, when it is problematic, expect that the appliance will not heat up.

If the problem is with the magnetron, there is no way that it can be repaired. It can no longer be salvaged, and hence, the best thing that you can do is to have it replaced. Again, this is a job that is best handled by the pros who have the necessary equipment and training.

Problem with the Door Switch

In the case of most microwaves, there will be three to four door switches. As the door is closed, the switches will actuate sequentially to ensure the door has been properly closed. If only one of these switches encounter a problem, the microwave will not heat.

Determining the problem will not be possible with just a quick visual inspection. A multimeter test needs to be conducted to be sure that there is continuity between the switches. If the light does not turn off even if the door is closed, this can be an indication that there is problem with the door switch, but that is not the case all the time.

Problem with the Thermal Fuse

In the case of overheating, the thermal fuse will automatically deactivate and will not supply power that is needed by the microwave to function. The outcome is that it will not turn hot. It is not usual for fuses to blow on their own. Sometimes, this is an indication of another problem, often with blown fuse.

To know if the thermal fuse comes with a problem, there will be burnt spots around the area. It will also possibly turn black. The fuse wire will also melt. If the problem is with the fuse, here is a short video that shows you how to handle the repair.

Problem with the Thermoprotector

Like the thermal fuse, this will also cut the power that is supplied to the microwave once it has overheated. It is a switch that has the main function of controlling the heat that gets into the microwave.

This can be caused not only by a problem directly with the thermometer, but can also be because of having a blown fuse. It cannot be repaired and instead, a replacement will be necessary. Multimeter testing is usually done to determine if the thermoprotector is indeed the problem on why microwave turns on but does not heat.

Problem with the Main Control Board

This is something that can rarely happen, but still, this is one of the reasons that you should know. It is important that you first consider the things that have been mentioned above before replacing the control board.


If microwave turns on but does not heat, do not be frustrated thinking that you need to waste your money buying a new one. Chances are, there are just some problems with its components. Many of these parts can be either repaired or replaced. In a nutshell, here is a rundown of the things that have been discussed above.

  • The problem can be the power diode, high voltage capacitor, magnetron, door switch, thermal fuse, thermoprotector, or main control board.
  • Diagnosis of the problem may sometimes be impossible with mere visual inspection. Oftentimes, multimeter testing is done to confirm the cause of the problem.
  • When there is a need for repair or replacement, it is best to always trust the pros. This is vital not only for safety, but also in making sure that the problem will be addressed properly.
  • Even if the microwave is turned off or unplugged, some components hold stored energy, just like a battery. This makes it important to be more careful in handling these parts.

Have you experienced the same problem with your microwave before? What did you do? Feel free to leave a comment below.

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