Running Microwave Empty

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A microwave provides us with a great and easy way to cook or warm up leftover food. Nevertheless, there are certain ways you need to use a microwave to maintain its functionality and be safe at the same time. Setting up the appliance is one thing, so is using it the right way.

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There must be thousands of questions we all ask ourselves daily regarding what would happen to microwaves in certain situations. Today, we are learning what happens when you microwave nothing.

One thing we know about microwaves is that they make use of radio waves at high frequencies to heat or cook your meal faster compared to conventional techniques. It is safe to say that this method of cooking or heating food is quite impressive. However, there is a limitation that comes with this unique heating method. For instance, what would happen if you accidentally ran a microwave empty? Well, read on to find out exactly what would happen.

Running a Microwave with Nothing

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The first thing you should know about microwaves is that they use a magnetron tube to make electromagnetic waves. These waves are the same ones we refer to as microwaves. How do these microwaves work? Well, these microwaves will hit your food and cause the water molecules present in your food to start vibrating. When these particles vibrate, they will cause some friction, which will then become heat and will in turn heat the food.

So, will running a microwave empty damage it? The truth is that if you run a microwave without anything, or if you heat something that does not contain some water molecules, then the electromagnetic waves will simply bounce around and back to the magnetron. As a result, the magnetron will start absorbing the same amount of microwaves it is producing. That might result in damage.

When you heat a microwave without anything in it, it will be fine in the first few seconds. The door, cavity, and tray will start absorbing energy and if you turn it off at that point, it will be okay. However, as it continues running, the door, tray, and cavity will begin to get hotter, even though it is still not at a critical point. But after it starts getting extremely hot, there will be excessive energy. That energy will start being reflected back to the magnetron and it will begin heating up at the same time. At that point, there might be a chance that a thermal fuse will be triggered, although that will depend on the appliance’s construction and size. In most appliances, you can reset that thermal fuse although it is not the same for all.

Also read: Can you Microwave Tupperware?

Poorly constructed appliances have a thermal runaway. Some parts of the appliance or location will superheat. That means it will get extremely hot to a point of liquefying porcelain. At some point, something will give out and there are chances that some plastic feature will burst into flames.
We recommend that you avoid running the microwave empty at all costs.

The Time it Takes

How long can you run a microwave empty before any damage can occur? Well, if you run a microwave without anything in it for a short period, such as a few seconds, it will be okay. You might notice that certain appliances will run when you close the door, especially if the appliance had some time left on the timer the last time you used it.

Before the appliance becomes completely damaged, you will notice that it will give out a certain burning smell.

In regards to the time it would take for an appliance to be damaged when running empty, it depends. The time it might take might vary from a couple of seconds to up to five minutes. It all depends on the appliance you are using.


So, how do you tell if your appliance is spoilt or damaged? There is a simple way. You can simply test the appliance by putting a microwaveable bowl with a bit of water inside the microwave and running it. A single minute will be adequate to prove if it still works. When you check the water after a minute, it should be hot. In case it is not, then the microwave is damaged and should be checked and repaired or replaced.

Additional Things to Avoid Microwaving

You can get the same damaging effects, even when the microwave is not empty. If you microwave some dry foods, you can expect the food to react in the same manner. Foods that do not have some water content should not be reheated with a microwave. Additionally, you should avoid any metal in the microwave because it will reflect the radio waves. In turn, it will create a different charge that will create other microwaves. The new waves will interfere with the first waves.

Safety Feature

We have established that it is not a good idea to microwave dry food or run a microwave empty. So, in case it happens accidentally? Will, it shut off automatically when it is overheated? A microwave will overheat unless it features some safety precautions and aspects that will make it shut off automatically.

A microwave with an automatic shut-off will turn off the heating elements once the temperature of the source of microwaves raises to a high level. That automatic shut-off feature is meant to prevent the machine from being damaged. It will prevent overheating, which would result in different types of failure.


  • What causes a microwave to suddenly stop working? Or Why is my microwave running but not heating?

  1. The microwave door isn’t closing properly. If the door is slightly ajar or open, the magnetron won’t be able to generate microwaves.
  2. The thermal fuse is faulty. A blown fuse will prevent electricity from flowing to the magnetron at all.
  3. The magnetron isn’t functioning.
  4. A blown diode can prevent electricity from flowing to the magnetron efficiently and, therefore, not allow it to function normally.
  • Can you put metal in a convection microwave oven?

Yes, you can put metal in a convection microwave oven. However, there are a few things to consider. Metal cookware may not be safe in a conventional microwave oven (unless specifically noted as microwave-safe), but it is safe to use in a convection microwave oven. Since convection-style microwaves have the ability to heat food like an oven, it should not spark or cause arcing when metal is placed inside of it. To be extra cautious, follow the manufacturer’s recommendations for your specific model when using this feature.

  • Are all microwave door switches the same?

No. Microwave door switches may look similar, but they have been designed to work with a specific manufacturer and model number. This is because each microwave switch has its own physical characteristics, such as length, width, and the size and location of the mounting holes. These factors vary between different brands of microwaves, so you need to find the microwave switch that matches your appliance. You can do this by comparing the information on your old switch against what’s listed on our website or in our catalog.


We have figured out that you can run a microwave empty, but only for a few seconds, or a few minutes depending on the appliance model. However, you should know that it is highly discouraged. The appliance will be damaged because the same radio waves will damage the magnetron that produces them. Avoid running it without at least some water in it.

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4 thoughts on “Running Microwave Empty”

  1. I installed an under the cabinets microwave to replace an existing unit. Saw no evidence of venting, so figured it was not an issue and neglected to rotate vent blower to blow into the room. Tried to cook a bag of popcorn. The first attempt produced hot corn kernels, but didn’t pop.
    Second attempt it didn’t heat at all.
    Have since gone back and corrected vent mistake, but it still won’t heat.what component is it likely to have damaged.….…thank you

    • Your microwave can be damaged in different ways. It requires different components in order to heat. Microwaves have a magnetron that will produce heat, allowing to cook. It also has a high voltage diode that gives the magnetron power. When these are faulty, the microwave will not heat even with power. You should also know that they are harder to access and you might require some assistance.

  2. Thank you for your microwave post. I accidentally ran my microwave empty. I thought I was starting the timer. Now the microwave has no power. The wall outlet and breaker are fine and I changed the fuse inside the microwave. Still no power. I can’t find another microwave to fit my built-in kitchen cabinet. So, I really want to fix this one if possible. Mine is a GE PEM31SM3SS. What might be the problem? Magnetron, Capacitor or Smart Chip Board? Any insights would be appreciated. Thank you very much.

    • There are several reasons why a microwave would stop working. It is true that a fuse would be a problem but there is more. The door switch might have a problem. The door latch assembly could also have a problem. They are made with plastic hooks that protrude out of the door and deliver a signal for the rest of the appliance to deliver power.
      Check the door latch and make a replacement if needed. Another problem could be the thermal fuse, which protects it from overheating. The ceramic fuse is another possible problem. This might be noted if the microwave does not turn on and the display does not have power too.


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