Tips & Tricks

Microwave Not Heating Food – Solutions

Microwave Not Heating

Microwave Oven

Imagine how happy our stone age ancestors would have been if they’d had a microwave oven to cook their food. Just by pressing a few buttons and setting the right temperature, they could have a mammoth stew in a minute or two. But everything has its own flaws. We are here to discuss and help you tackle these problems regarding your Microwave Not Heating Food. So that we are lucky to have microwave ovens by our side. Late to work, no time for breakfast? Toss that frozen patty in the microwave oven and have your food cooked in an amazingly short amount of time.

How Microwave Oven work?

Microwave ovens could be one of the greatest inventions of the 20th century. But how exactly do microwave oven work? Let’s explore the science behind it.

Microwaves are electromagnetic which fall in between radio waves and infrared waves. Cooking microwaves have a frequency of 2.45 gigahertz and a crest-to-crest distance of around 12 cm. Food molecules, particularly water molecules, absorb waves at these frequencies. This absorption of frequency creates friction in the water molecules which results in heating the food.

An amazing fact to state here is that microwaves don’t interact with plastic, glass or ceramic. This is why only the food is heated. So that explore why, in some cases, the microwave will not be heating food.

Reasons Behind Microwave not Heating Food

  1. Defective Door Switches
  2. Burn-out Diode
  3. Multifunctioning Magnetron
  4. Defective High Voltage Capacitor
  5. High Voltage Transformer Failed
  6. Thermal Fuse
  7. Thermoprotector Tripped
  8. Defective main control board

To fix

Fixing Issues Microwave not Heating Food

  • Multimeter
  • Long Screwdriver
  • Short Screwdriver

Before we dig into fixing these major issues, make sure to check on the following basic settings;

  • Set time for several hours for cook. Timer settings are common in modern microwaves, allowing you to have dinner ready when you get home. Make sure you didn’t just say it would be ready in 5 hours.
  • Check the wrong setting/mode. Check to see if you’ve just set it to the lowest power setting. Or that you’re attempting to reheat a fully frozen supper on the ‘keep warm’ setting.
  • Something that not microwaved. The common misconception is that a microwave ‘heats’ everything. Instead, they heat the water within the food. It’s doubtful that you’ve tried to microwave dry food. Use a liquid test to find out.
  • Voltage Not working Properly. Make sure to check if the voltage supply is working properly before you mess up the settings with your microwave oven.

A Defective Door Switch

A defective door switch is one of the most common problems where usually the door locks wouldn’t close the door. Because these locks lose their sturdiness with passage of time or when the door is opened or closed by force. To fix this issue, you’d need to check if the problem is with the switch or the door locks only. Open the casing of the oven by unscrewing it. You’d locate the switches where the door locks get hitched.

Plug the microwave oven in and carefully turn on the switch with the help of a screw driver. If the microwave turns on, then the problem is with the door lock, otherwise you’d need to change the switch entirely. To fix the door lock issue, you’d need to open up the door panels. Gently un-lock the panels on the door with a screwdriver. Clean up the inside of the panels and un-assemble the lock. Try to re-assemble the lock in its place after cleaning it and placing the spring in its place. Don’t put too much pressure and be gentle while working with it. As you fix the lock in place, plug in the electric power and check if it’s working. Make sure you’ve assembled everything perfectly and then put the casing back in its place. Tighten the screws and you’re good to go.

A Burn-out Diode

The microwave diode transforms the transformer’s alternating current (AC) to direct current (DC), roughly tripling the voltage to approximately 5,000 volts. A burn-out diode will result in Microwave Not Heating Food. Use a multimeter with a 9-volt battery to test the diode.

Connect the high impedance of a 9-volt battery to the black lead while holding it against the opposite end of the diode. You also need to connect the red lead to the positive terminal of the battery. Making sure the diode has its continuity in one direction, there is no problem with the diode.

Multifunctional Magnetron in microwave

In the oven, a magnetron is responsible for producing microwaves, which heat the food. Though the magnetron has a malfunction, it will result in Microwave Not Heating Food. To fix the problem, you’ll need to use a multimeter or an ohmmeter to troubleshoot it. Inspect the magnetron for cracking, burning out, or faulty connections. Replace the damaged magnetron with a new one or make the necessary connections.

Defective High Voltage Capacitor

Any issue with the HV capacitor will have an impact on the entire high voltage circuit’s operation. Only a specialist VOM meter with capacitance testing capability can test the HV capacitor. Even when turned off, the HV capacitor can hold a charge of around 3000 volts. As a result, it’s usually preferable to leave it to a trained professional to inspect. Replace the capacitor in case of any damage as this part cannot be fixed.

High Voltage Transformer Failed

Stop using your microwave if the high-voltage transformer is causing electrical sparks. Continued usage of the microwave could result in further damage or possibly a fire. If you see an electrical arc and a burning odour, you’ll most likely require a new transformer. If there are no obvious symptoms of damage, use an ohmmeter to identify any damage that isn’t evident. Replace the transformer if there is a problem.

Thermal Fuse

One or more thermal cut-outs, sometimes known as thermal fuses, are employed in microwave ovens to prevent overheating. The power to the controls or control outputs is turned off if the thermal cut-out fails. Remove the cabinet and unplug the unit. Remove the wires from the cut-out terminals or the thermal fuse. If there is no continuity, use a multimeter to check it and replace the component. Make sure the cooling fan is turned on and the airflow isn’t obstructed.

Defective main control board

The touchpads on your microwave oven may not respond but the display lights up, this is the result of a problem in the main switch control board. The membrane switch is powered by a low voltage generated by the control board. The voltage signal is returned to the control board when a pad is pressed. You’ll need to switch off the power and remove the cabinet and control assembly to replace it.


  • What would cause a microwave not heating food?

The magnetron, a door switch that isn’t supplying electrical continuity, or a high voltage diode is the likely culprits if your microwave oven isn’t heating.

  • Is it worth fixing a microwave not heating food?

If you like fixing some stuff or you’re a fan of DIYs, you can give a chance to fixing your microwave before taking it to an electrician. Fixing some minor problems can give a better and longer life to your appliances.

  • How do I know if my magnetron is working?

Touch the magnetron’s terminal and its metal case individually with an ohmmeter set to its highest readings. Your ohmmeter does not need to be replaced if it displays an infinity reading.

  • Can you reset a microwave?

A microwave is reset when you plug out the power supply. To hard reset the settings, you can the time of the day.


Microwaves have become ingrained in many of our daily routines. And when they break, it can throw our plans for the day into disarray. There are a number of factors that could be causing your microwave to not heat up and cook your food.

This article outlined a number of issues that could lead to a defective microwave. There isn’t a quick answer for microwave problems. Before doing anything with your microwave, always consult a competent electrician.

the authorSophia

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