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Microwave Not Heating Up: Causes and Solutions 

by Nick Evans | Last Updated: March 15, 2022

Microwaves heat food by causing water molecules to vibrate. Therefore, microwaves don’t typically heat up. Instead, they heat the food or beverage that’s in the microwave. Still, sometimes microwaves don’t work the way they’re intended to. In these situations, understanding why your microwave isn’t heating food is important. Letting your microwave break can cost you money in repairs and increase your likelihood of ordering takeout, which is not cheap.

If you’ve noticed that your microwave isn’t heating meals anymore, you’re in the right place. We’ll take you through what you need to know about your microwave and some of the reasons it won’t heat food or beverages.

Moreover, we’ll provide you with some simple solutions and let you know when it’s time to call a technician or replace the microwave. Read on to learn more about why your microwave is not heating.

Microwave Components 

Before we take you through some of the common causes and solutions of your microwave not heating things, it’s important to understand what a microwave does.

There are several components in your microwave that work together to heat food. These components vary in importance and durability and some are more likely to break than others.

Most microwaves are made with the same features. These are listed below.

If any of these components break, your microwave won’t heat food properly. In some cases, your microwave won’t work at all if there is an issue with the power system.

How a Microwave Works 

Microwaves are less complex than many people think. These appliances are designed to heat food and beverages with electrical energy that’s converted to microwaves. Microwaves are high-frequency radio waves that cause water molecules to vibrate.

When the water molecules vibrate, the friction generates heat. For this reason, anything that contains water can be heated in a microwave. On the other hand, if something doesn’t have water molecules it can’t be heated in a microwave.

For example, a plate without food or water in the microwave won’t heat up. This is also true for the heating chamber.

In summary, microwaves convert electrical energy into microwave radiation that heats water molecules by causing them to vibrate. The vibration causes friction heat and cooks your food.

Read Also: White Smoke From Microwave (How to Fix)

How to Determine Your Microwave Is Not Heating 

There are a handful of ways to determine if your microwave is not working properly. That said, people also make mistakes. These mistakes can lead you to believe that your microwave is not working when it’s working fine. Here are a few factors to consider before calling a professional or trying to fix your microwave.

Check the Timer and Settings 

First and foremost, you want to start with the control panel. If you’re sure that the microwave is plugged in and operational, this is the first test you can perform.

Take a look at the panel and make sure it’s not set to something like “warm” or “defrost.” Using a microwave on these settings will cause it to keep things warm and not cook them. Some microwaves also have timers that tell it when to begin heating something.

If you accidentally set the timer for 3 hours, it might not turn on until you turn that setting off.

Another thing to check is the power setting. This is important if you have a variable wattage microwave because lower settings take longer to heat things. In fact, your microwave might not be heating because you have it on a lower setting.

Make Sure the Item Is Microwave-Safe 

The next thing to consider is what you’re trying to microwave. Because microwaves heat things with microwave radiation, some things can’t be microwaved. This is the case when you’re trying to microwave something that’s dry or lacks water. One example would be a steak that’s been freeze-dried. Because the steak lacks water, you can’t heat it in a microwave.

If your microwave is not heating and it’s not caused by one of these factors, it’s time to evaluate some causes and solutions.

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Reasons Your Microwave Is Not Heating

Microwaves are complicated appliances with a lot of components that work together to cook food. For that reason, some of these components can break and prevent the microwave from working properly.

We’re going to take you through some of the reasons why your microwave is not heating. We’ll also show you how you can diagnose these issues. 

Door Switches 

Every microwave has a door switch. In fact, most microwaves have more than one door switch (some models have as many as 5). Door switches are responsible for locking the microwave and preventing the microwave from operating when the door is open.

When the door is not locked, a microwave won’t turn on because microwaves pose a threat to your health if the door is open.

Most microwaves have a light. The light is on when the door is open, so if the light stays on when the door is closed the door switch is not working. If this is happening to your microwave it won’t heat food or turn on.

Therefore, you’ll have to replace the door switches to solve the problem. If you need to replace the door switches you need to look up the brand and model number.

The model number can be found on the back of the microwave and the brand is typically located on the face near the control panel. With this information, you can order replacement door switches and use your owner’s manual for instructions on how to replace them.

High-Voltage Diode 

The high-voltage diode is a component that converts A/C power to D/C power. A/C power needs to be converted for the magnetron to function properly. When this component fails you’ll hear a humming sound. If you end up checking the component and removing it from your microwave, it’s easy to notice that it’s burnt out.

That said, sometimes it’s hard to notice if the high-voltage diode is not working properly. To test the high-voltage diode you can use a multimeter. The device is designed to channel electricity in a single direction.

When testing the high-voltage diode, there should be more resistance on one side than the other. If the voltage is the same on both ends, the high-voltage diode is not working properly. The good news is that you can find replacement parts for a low cost and replace them on your own.

Magnetron 

The magnetron is the device in your microwave that converts electrical energy into microwave radiation. While the magnetron is a durable component, it uses a lot of electricity and can blow a fuse if it’s not working properly. A blown fuse will result in the magnetron not getting power and cause the microwave to not heat food or beverages.

Like the high-voltage diode, the magnetron can be tested with a multimeter. A functioning magnetron should have a resistance that’s between 2 and 3 ohms.

If your magnetron does not have this resistance, there’s a good chance it’s broken. While you can replace the fuse on your own, we recommend working with a professional to replace the magnetron. Replacing the fuse can lead to problems in the future if the magnetron is still broken.

Thermal Fuse and Thermal Protector 

Microwaves have a thermal fuse, which is used to prevent the appliance from overheating. While most microwaves use fuses, some advanced models use thermal protectors.

To determine what your microwave uses we recommend checking your owner’s manual or looking up your microwave’s product information online.

While you can replace the thermal fuse or thermal protector on your own, finding the parts is easier said than done. In most cases, you have to get fuses from the manufacturer. Once you have the parts, it’s as simple as removing the blown fuse and inserting the new fuse. As a safety measure, microwaves with blown thermal fuses won’t turn on to prevent damage to food, yourself, and the microwave.

High-Voltage Capacitor or Transformer 

A high-voltage capacitor is what most modern microwaves use to store electrical energy. These devices are also known as transformers. In fact, most microwaves use smaller versions of the transformers that you see on power lines.

Microwaves need to store electrical energy before converting it to the magnetron to prevent an abundance of power usage.

While high-voltage capacitors can be replaced, these parts are complex and expensive to repair. For this reason, we recommend getting a new microwave if you have an older appliance.

On the other hand, some newer and more expensive microwaves can be repaired with the help of a professional and the right components. You can determine if the capacitor is damaged by smelling the microwave. If it smells foul or like something is burnt, it’s likely a capacitor problem.

Control Board 

The control board is responsible for controlling the microwave. It’s the brain of the microwave and if it’s not working you won’t be able to do anything. In some cases, it might only partially break. Some examples of this include only being able to set the timer. You can test to see if your control board is broken by messing around with your microwave’s settings. If nothing works there’s a good chance that the control board is not working.

If the control board is broken we recommend replacing the microwave. Control boards are complex components and can be expensive to replace. Therefore, getting a fresh microwave is often the best alternative. 

When To Call a Professional 

Microwaves are not simple appliances. There are a lot of complex components and many of them can break with frequent usage. If your microwave is no longer under warranty and you can’t fix it on your own, it’s time to call a professional.

In some cases, professionals can repair your microwave for a good price. On the other hand, microwaves can be replaced for a low cost (in some cases), so if your microwave is too far gone we recommend replacing it with a newer model.

Final Thoughts 

When your microwave breaks it puts you in a bad position. You’ll have to wait longer for otherwise quick meals to cook or order expensive takeout. The good news is that many microwaves can be fixed with a little time, knowledge, and patience. On the other hand, replacing your microwave or working with a professional is also a viable option. 

That said, we recommend diagnosing the reason your microwave is not heating on your own before reaching out to a professional. This can save you time and money and let you know if replacing the microwave is the better alternative.

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10 appliance hacks to help you save up to $100 per month on your electric bill.

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