What Can Cause Microwave Not To Heat and How To Fix

What Can Cause Microwave Not To Heat

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A microwave is one of the most useful kitchen appliances you will not miss in a modern kitchen. It cooks, and heat food fast. Hence, it is a convenient appliance you can have at home. Like any other appliance, you might wake up only to find it has an issue. In this case, you realize your microwave is not heating when you hit the start button. What do you think in this case?  Do you panic and throw it away? NO! There are possible solutions to that. But before that, desire to know what can cause microwave not to heat. Keep reading to know the causes and how you can fix the problems.

7 Things That Can Cause Your Microwave not to Heat

If your microwave is not heating, know there is a cause for that. You may only know how to fix the problem if you discover the cause. Some of the causes are as follows.

Faulty diode

A diode is a microwave component whose role is to power up the magnetron tube and enable microwave radiation production. A burnt-out diode in a microwave makes the magnetron receive little or no power. Thus, low microwave radiation ensures enough heat in the microwave to heat or cook food. The best way to fix this issue is to replace the diodes.

Broken magnetron

This is another common reason your microwave is not heating. The role of the magnetron is to create the microwaves responsible for heating your food. Running a microwave device with no food inside can damage the magnetron. Alternatively, this can arise due to broken magnets and loose connections.

You can use different ways to tell your microwave appliance has a broken magnetron. The most common is having the microwave running but not heating your food. On the other hand, your microwave can be running but making abnormal noises. Also, you can find the two magnets in the device broken or a discolored metal cylinder.

Faulty door switch

A microwave has 3-4 door switches.  Once you close the door, the switches become active and tell the microwave it is safe to start. When the switches are defective, the machine will not heat.

Luckily, it is easier to tell that the door switch of your microwave is faulty. One of them is having the turntable not turning and the microwave not heating up. On the other hand, a microwave light will not come on once you open the door.

Several things can cause your microwave’s door switch to be faulty. The major one is slamming the door. Another cause for this is faulty parts or forcing the door closed.

Failed high-voltage transformer

You can tell that the transformer of your microwave is failing in several ways. One of them is having an electric shock feeling once you touch your microwave’s handle or door. Other signs include your transformer emitting a high-pitched sound or a burning smell. A microwave oven uses a high-voltage transformer to produce energy for cooking or heating your food. Thus, if it fails, you will experience a burning smell.

Use a multimeter with a capacity tester or VOM to tell if your microwave’s capacitor is working. The solution to a faulty capacitor is a replacement.

Blown thermal fuse

Another reason your microwave can stop heating is a cavity or blown a fuse. The role of a thermal fuse is to interrupt the power supply whenever a microwave overheats. Use a multimeter to test if the fuse is working or not.

A defective main control board

The role of a main control board in a microwave is to regulate the power supply in other components of the device. When the board is defective, the entire microwave stops working. In general, it is tough to tell that the main control board of your microwave is not working. This is mainly if you are not an expert in microwaves. Therefore, looking for a professional to check this for you is wise.

Tripped Thermo protector

A microwave features an integrated thermal protector. When the device overheats, the thermo protector cuts power to protect against damages that might arise from overheating. Tripping the thermo protector causes the microwave not to heat. Other times it will not start. The tripping mechanism can help save a life, especially if you accidentally forget your food in the oven.

Using a multimeter is an excellent method of telling if your thermo protector is working. It tells you that the protector is faulty and needs replacement if it does not have continuity.

How to Fix Microwave Not Heating Food

Now that your microwave is not heating your food, the next action is to fix the problem. Gladly, there are issues you can fix yourself. The most complicated ones demand the help of an expert. Whether it is you or an expert fixing a microwave that is not heating food, below are some of the steps to consider.

Replace the Faulty voltage diode

When you confirm your microwave is not heating because of a faulty diode, the next is to have them replaced. To replace the diode, follow the steps below.

  1. Unplug your microwave from the power supply.
  2. Remove the turntable of your microwave and unscrew the panel that covers the diode.
  3. Before that, discharge the capacitors for safety purposes.
  4. Remove the diode screw and disconnect it from the microwave’s capacitor.
  5. Install your new diode by making sure it features the right polarity.
  6. Assemble back your microwave and plug it in back.
  7. Replace the magnetron

In a microwave oven, the magnetron is a crucial component. It provides the heat used in cooking or heating your food. A broken magnetron can cause the fuse to blow up. Which in return can make other components in the microwave fail. Use the steps below to repair the issue of a broken magnetron in your microwave.

Unplug your microwave from the power. Discharge the high-voltage capacitor and test using a multimeter.  At this moment, make sure you disconnect all the attached wires. A normal magnetron should give a continuity of 2-3 ohms. If you obtain that, continue probing the metal casing with your multimeter. Something is not right if you get a zero on display. Replacing a magnetron that does not show continuity is the best solution.

Replace faulty door switch

A faulty door switch is a result of slamming the door harder. Else, your microwave may be old enough to develop such a problem. If your microwave is not heating food because of a faulty door switch, take the steps below to fix the problem.

When you realize your microwave is not heating your food and suspect the issue is on the door switch, the solution is not slamming the door further. This only causes further damage. First, take your time to re-check the issue to ensure you are right about it. 

After confirming your microwave is not heating food because of the door switch, unplug it and test it using a multimeter. Then, depress the actuator button to check the switch. If you realize there is no continuity, the best solution to this is replacing the switches. When checking this, make sure the door is hooked. This is because it triggers the door switch to work in the right way.

Failed high-voltage transformer

It is easy to tell that the high-voltage transformer of your microwave has failed. This is because it arcs and produces an off-putting smell. It is hard to replace a microwave’s control board, but the same applies to the transformer. It is wise to replace the entire microwave if it is not heating food because of a failed high-voltage transformer.

Replace the Blown thermal fuse

If you find out your microwave is not heating because of a thermal fuse, the solution is replacing it. Even though this is simple, note that the fuses used in a microwave differ from the ones in the home fuse box. Therefore, you must take your time to look for the specific one for your microwave.

Replace the entire microwave

This is a solution to a damaged control board of your microwave. In a computer, we have the motherboard; in a microwave, there is the control board. When it fails, you can be sure your microwave will fail completely. Buying a new microwave is the best solution to a damaged control board because replacing it is complex. However, if your microwave is new, look for an expert to do the replacement.

Why Does My Microwave Not Heat Evenly

Like we said initially, a microwave oven is an essential kitchen appliance every homeowner should possess. This is because of the many purposes it serves. For instance, you can use a microwave to defrost meat as well as make your dinner. Nowadays, some people are complaining about their microwaves not heating food evenly. This post outlines some reasons why your microwave is not heating evenly. Take a look!

Cold zones

Once microwaves are fed into a machine, a wave pattern is formed. At times, the waves tend to hit one another and form a cold zone. Heat is not created in such a zone.

Even though microwave technology is advancing daily, it is impossible to avoid cold zones. But rotating the item can prevent this from becoming a big issue. Hence, heat will go through it evenly.

When your microwave plate is not spinning or your item has not sat on the plate properly, chances are higher that parts of your food will be sitting in the cold zone. This makes it not heat evenly.

Unfortunately, it is impossible to identify where the cold zones are. The solution is putting a packet of marshmallows in the microwave, lying evenly. Afterward, de-activate or remove the rotating plate. Put the microwave on for a short burst.

Varying food densities

If you cook food with different densities together, they will not heat evenly. Note that even a single food can have varying densities in various parts. This is mainly when the dish has several ingredients. An example is when you defrost your meat, and the center remains unfrozen.

The best thing you can do to prevent this is to distribute food pieces evenly on the dish. Also, try everything possible not to cook foods with different densities together. When defrosting your meat, make sure they are in small pieces and defrost while covered at room temperature.

Frequently Asked Questions (FAQs)

Why is my microwave running but not heating?

The common reason your microwave can be running and not heating your food is a broken magnetron. The magnetron’s role is to create the microwaves responsible for heating your food.

Why does my microwave stop heating after a few minutes?

If a microwave has high voltage parts inside getting too hot, the outcome is having it overheat and shut itself down. You can prevent further overheating by activating the thermal cut-out switch.

Why is my microwave only heating for 3 seconds?

A microwave that runs for a few seconds and shuts off will likely result from a loose or defective door switch. Overheating or arching of the door switches sometimes makes the microwave not run efficiently. You realize some microwaves feature a gasket or seal around the door. If they break down, the microwave stops functioning immediately.

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