Like any other electrical appliance, a microwave can fail and usually does so when you need it most.
The most popular reason a microwave isn’t heating food is that the magnetron is broken and needs replacing. Faulty door switches are also a common problem and are much easier to diagnose and replace when they have failed.
It is important to note that if you are not a trained electrical technician, you should never attempt to open the back of your microwave oven. Even after your microwave has been unplugged for many hours, the parts still have enough energy to give you a fatal electrical shock. Always refer the repair to someone who is qualified to handle a microwave unit.
In this guide, I’ll try to help you diagnose your microwave problem safely and find out why your microwave is not heating.
1. Faulty Magnetron Switch
The most common problem is a faulty magnetron. When in operation, the magnetron utilizes high-voltage electrical power to generate the microwave frequencies that heat up your food (even with microwave toaster combos).
When it has gone bad, your microwave will appear to work but may make a buzzing sound while rotating the food. But the most important tell-tale sign is that your food remains cold.
- Cause: Aged magnetron or faulty magnetron switch.
- The Fix: If either the magnetron or the switch is broken, you need to contact a licensed technician to make the replacement.
2. Faulty Door Switch
Microwaves typically have 3 door switches. When you close the door, the switches activate and tell the microwave that it is safe to start.
The unit will not turn on if any of the three switches are defective.
The most common way to identify this problem is when the light inside the microwave does not go out when the door is closed.
- Causes: Slamming the microwave door (especially on small microwaves and microwave drawers), worn or faulty parts.
- The Fix: It could be as simple as a piece of worn down or broken plastic. Sometimes it’s an electrical issue that requires a licensed technician to identify and repair.
3. Microwave Power Failure Error
You may notice that your microwave displays ”PF” or ”8888” instead of the usual display after a power failure.
The ”PF” stands for “power failure” and the ”8888” is also a code indicating power failure.
- Cause: The microwave lost power abruptly. This is common during power outages.
- The Fix: This error is a temporary fault that you usually do not have to worry about. Simply press the ”CLEAR” button, or refer to your manual for instructions to do so for the error to disappear. Remember to reset the clock after clearing the error. If the error happens again randomly without a power outage, you will need to contact an electrician.
4. Faulty Capacitor
If you try to use your microwave and instead of heating your food, it just makes a buzzing noise, then it’s likely that it has a defective capacitor.
Microwaves have a high-voltage capacitor, a device that stores electricity and is essential to the unit’s operation. If the capacitor is faulty, your microwave oven cannot operate normally.
- Cause: Under normal conditions, it’s likely the part is old or has become faulty.
- The Fix: This problem requires a skilled technician to 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 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 be fatal even after the microwave has been turned off and unplugged for hours.
5. Faulty Thermoprotector
Sometimes, the thermoprotector can go bad and have similar symptoms as a bad magnetron. Everything appears to be working without issue, but your food is just not heating.
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 the heating power.
- Cause: Tripped fuse or faulty thermoprotector.
- The Fix: In some cases, the device might just need to be reset and not replaced.
6. Dimming Microwave Light
When using your microwave with lower power settings for tasks such as defrosting or reheating, many microwaves may dim the lighting.
Try microwaving a cup of water at 100% power to test this. You should see that your microwave lights up normally because it’s operating at full power.
- Cause: Settings, old parts, or failing parts.
- The Fix: Try turning off any power-saving settings from the menu and try again. If the light is still flickering, there is probably an issue with the bulb or wiring.
7. Faulty Power Diode
If your problem is a buzzing noise while microwaving, but your food still heats up, a diode could be the problem.
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 doubles the voltage.
This power is then fed to the magnetron for conversion to microwave energy.
- Cause: Old or faulty parts.
- The Fix: You will need to contact a licensed technician to test the diode.
8. Faulty Triac
If your microwave only cooks food on full power, the triac controller switch may be to blame.
Another symptom you might see is your microwaving immediately turning on when you close the door. This would indicate a short somewhere, and you stop using it and unplug it until it can be repaired.
- Cause: Faulty controller switch.
- The Fix: A licensed technician will be able to diagnose and fix this problem.
9. Faulty Main Control Board
Although this is not a common problem, the main control board can be defective.
If the control board has a problem, you might find that you cannot enter the menu or save your desired settings. For this reason, you need to consult the dealer because it is likely to be a manufacturing fault.
- Cause: Faulty control board.
The Fix: If you’re out of warranty, you’ll need a technician to replace the board. But at that point, replacing your microwave with a new one might be cheaper.