Why Is My Microwave Not Heating?

Just like any other electrical appliance, a microwave can fail and it usually does so when you need it most. In this article we will try to help you diagnose your microwave problem and find out why your microwave is not heating.

It is important to note that if you are not a trained electrical technician, you should never attempt to open the back of a microwave oven. There is a great danger from electrical shock even after the microwave has been unplugged for many hours. Always refer the repair to someone who is qualified to handle a microwave unit.

Microwave Problems & Troubleshooting

Faulty Door Switch

ProblemMicrowaves usually have 3 to 4 door switches. When you close the door, the switches activate and tell the microwave that it is safe to start. If any of the three switches are defective the unit will not work.

The most common way to identify this problem is when the light inside the microwave does not go out when the door is closed.

Cause – Slamming the microwave door, or forcing the door closed for touch based drawer microwaves, worn or faulty parts.

Fix & Repair – It could be as simple as a piece of plastic that has worn down, broke, or an electrical issue that requires a licensed technician to identify and replace.

Microwave Power Failure Error

Microwave Error 8888

Problem – After a power failure, you may notice that your microwave is displaying is displaying ”PF” or ”8888” instead of the usual display. The ”PF” stands for “power failure” and the ”8888” is also a code indicating power failure.

Cause – The microwave lost power. Common during power outages.

Fix & Repair – This error is a temporary fault that you do not have to worry about or refer to a technician. You just need to press the ”CLEAR” button for the error to disappear. Once you remove the error, you can then proceed to reset the clock if you so wish.

A Faulty Capacitor

Problem – You attempt use your microwave and instead of heating your food it just makes a buzzing noise. It is likely that it has a defective capacitor. A capacitor is a device that stores electricity. A microwave oven usually has a high-voltage capacitor that is central to the operation of the unit. If the capacitor is faulty, your oven cannot operate normally.

Cause – Old and/or faulty parts.

Fix & Repair – This problem requires the intervention of a skilled technician to remove the capacitor and test whether it is the source of the problem. If the capacitor is the problem, you need to have to be replaced.

It is important to note that anyone handling the capacitor should first discharge it before testing. The capacitor is one of the most dangerous parts of a microwave. The capacitor has the ability to hold enough electricity (like a battery) to kill someone even after the microwave has been turned off and unplugged.

Faulty Magnetron Switch

Problem – The microwave appears to work but makes a buzzing sound while rotating the food and the food remains cold.

Cause – Aged magnetron or faulty magnetron switch.

Fix & Repair – The Magnetron is responsible for heating the food you put into the microwave. When in operation the magnetron utilizes high voltage electrical power to generate the microwave frequencies that heats up the food. If either the magnetron or the switch is broken, you need to contact a licensed technician to make the replacement.

Faulty Thermoprotector

Problem – Everything appears to be working without issue but the food is not heating.

Cause – Tripped fuse or faulty thermoprotector.

Fix & Repair – The Thermoprotector is a switch that is meant to control the amount of heat in a microwave. If the temperature within the unit exceeds a certain point the device cuts off power.

For obvious reasons, the microwave oven cannot operate if this essential component is not working. In some cases, the device might just have tripped a fuse due to overheating and needs to be reset and not replaced.

Dimming Microwave Light

Problem – Sometimes the light is dim and sometimes it looks fine. Sometimes it dims in and out.

Cause – Microwave settings.

Fix & Repair – When using your microwave with lower power settings for tasks such as defrosting or reheating many microwaves will also dim the lighting. To test this, try microwaving a cup of water at 100% power. You will notice that the microwave will light up normally because it’s operating at full power. If the light is flickering there is probably an issue with the bulb.

Faulty Power Diode

Problem – Buzzing noise while microwaving but food still heats up.

Cause – Possible faulty power diode.

Fix & Repair – A power diode is an electrical device that works by allowing current to pass in one direction only. The device converts electrical power to DC and effectively doubling the voltage to 5,000 volts. This power is then fed to the magnetron for conversion to microwave energy. You will need to contact a licensed technician to test the diode.

Faulty Triac

Problem – The microwave only cooks food on full power.

Cause – Faulty controller switch.

Fix & Repair – A licensed technician will be able to fix this problem.

Faulty Main Control Board

Although this is not a common problem, it is possible for the main control board to be defective. If the control board has a problem, it means that you cannot enter your desired settings. For this reason, you need to consult the dealer because it is likely to be a manufacturing fault.

Microwave Repair Options

  1. If your microwave was recently purchased you might be able to return it to the store where you bought it.
  2. If it is under warranty you might be able to have it repaired without cost to you.
  3. If your microwave unit has passed the warranty period, you will need a local electrical technician to service it.

While we hoped to have offered some DIY fixes for you, the nature of these microwave problems is best left to a professional. With the price of microwaves these days, it might just be better to purchase a new one than to pay a technician to fix your old microwave.

Did you enjoy this guide? Let us know in the comments with your tips and microwave fixes.

5 thoughts on “Why Is My Microwave Not Heating?”

  1. I have a GE microwave, that on the inside, looks almost exactly like yours in the video, except that the magnatron is oriented with the plug 90 degrees to the left, yours is pointed down.

    The magnetron TCO has a partially melted and charred plastic connector cover on the left side as you look at it.

    The microwave has been somewhat intermittent for a few weeks…..at first, it would buzz a bit more loudly than the normal hum, the light would not come on, and the table would not rotate. Thinking that the table rotating mechanism was stuck, I would rotate the table back and forth, and attempt to turn it on, it did not always work, but eventually every morning, by going through that process, it would finally start and work well for the whole day. Every morning I had to repeat this process to get it to work.

    So, I decided to take a look and attempt to fix it. First, I took out the turntable motor, and tested it….perfect….put it back in, and tried it out. Huge LOUD BUZZ!
    No, light, no turntable rotation. Smelled the effects of heat, like something melting….took the cover off, discharged the cap, (no sparks or anything), and observed the melted connector on the mag TCO. Cleaned it well, re-attached and put cover back on. Tried to operated it again, and eventually the light came on and the table rotated consistently, but would not heat up water at all… the horrible loud buzz is still present, light comes on, table rotates, no heat….

    Any ideas, thanks!

    • Hey Steve!

      It sounds like your microwave was already due for a replacement and we strongly recommend it. The risk of a starting a fire is a strong point to consider letting go of your current microwave. Depending on your model some microwaves can be a hefty investment, but it’s small in comparison to the damage that could be done to your home or life.

      Anytime electronics char, melt or smell, a whole line of items would most likely need to be replaced and end up costing a lot of money… perhaps as much as new one that would come with a manufacturers warranty and updated technology.

      Again, we recommend that you replace your microwave or take it to a specialist in your area.

      Cheers

  2. Good day to you all.
    I have a new Morphy Richards microwave although I have had it for several months now and then I decided to start using it the day before yesterday to heat up food. I followed the process of installation using the manual that came with it. The light, turntable and timer works fine but it does not heat up food… Tried several times to no avail even had to try boiling water… It does not heat up at all. Am confused. Please what do I do?

    • I have a new Midea microwave from an online store. I followed the process of installation using the manual that came with it. The light, turntable, and timer work fine but it does not heat up food. Contacted the store, and they responded could not take it back, Please what do I do?

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