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

Problem – Microwaves 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

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.