Microwave Fan Won’t Turn Off – 7 Causes and Fixes

Everything seems to be working fine. You haven’t experienced any problems with your microwave so far. But then all of a sudden the microwave fan won’t turn off. Should this be a cause for concern or is this a normal occurrence from time to time? What exactly causes the microwave fan to run continuously?

In this article, I’ll discuss a common issue that you might suddenly experience with your microwave and how to fix it.

Function Of A Microwave Fan

The function of a microwave fan is to protect all of the electronic components in your microwave from excess heat. The fan shuts off automatically once the temperature around the control panel is below 150 degrees Fahrenheit. 

There is a built-in thermostat in the microwave oven that registers the current temperature around the control panel and automatically turns the fan off or on depending on whether there is any excess heat.

7 Reasons Your Microwave Fan Won’t Turn Off

It’s frustrating to hear your microwave fan whurring and not stopping, and to add to the pain there are a number of causes. So, we’re going to have to work through each. Below is a list of potential causes in order of the probability they are triggering the fault. Follow each troubleshooting guide from number 1 down to number 7 and you will find the issue, along with advice on the action to take next.

1. Overloading The Microwave

It’s not a good idea to put more food on the turntable plate than your microwave can handle. If you do, the microwave oven will have to in a sense work harder to heat all the food you put in it. This results in the fan continuing to work even after you take the food out.

Power Off For 30 Minutes

Putting too much food in the microwave from time to time likely won’t cause any serious trouble. However, you should be mindful and not overload the microwave. In case you do, and the fan won’t turn off, you should give the appliance time to cool off. The best way to do this is to power off the microwave for at least 30 minutes.

2. Clogged Grease Filters, Air Filters, or Vents

If the air filters or grease filters in your microwave get clogged with dirt, they can cause the fan to run continuously. In case it often happens that the fan works longer than it should, you should check the grease filters, air filters, and vents and clean them if necessary.

Clean Filters and Air Vents

To clean the grease filter, you’ll need a sponge, baking soda, and dish soap. First, unplug your microwave and find the grease filter, which is located underneath the appliance and looks like a metal mesh rectangle. Use hot water and dish soap to clean it thoroughly. In case it’s really dirty, you should use baking soda to clean it more effectively. Use the same process to clean the vent, located at the top of the microwave face frame.

Air filters aren’t designed to be washed since water would prevent them from performing their function. Instead, you should replace the air filter if it’s not working properly.

3. High Kitchen Temperature

Despite there being nothing wrong with your microwave oven and any of its components, the fan might not turn off in case the temperature in your kitchen is too high. This can especially be the case in the summer. In this case, the fan will turn off when the thermostat in your microwave registers an even temperature between the kitchen and the microwave.

Reduce Ambient Room Temperature 

To avoid a bigger problem developing with your microwave, it’s recommended that you lower the ambient temperature in your kitchen. Just turn on a fan or your air conditioner and you’ll be less likely to experience an issue with your microwave fan.

4. Faulty Damper Assembly

The damper assembly is a part of the microwave that’s tasked with enabling the air to flow outside. It also prevents air from coming into the microwave from the outside. Depending on the model of your microwave, the damper assembly will direct airflow from either the rear or the top of the appliance. This component is made out of metal or plastic.

The damper assembly can stop working properly over time, which in turn causes the microwave fan to run continuously. In case your microwave fan won’t stop running, you should inspect the damper. You can find out how to do this in the section below.

Inspect Damper Assembly

The damper assembly won’t be able to perform its function in case it’s broken or damaged. You can check for any damage yourself using the following tips:

1. The first step involves disconnecting the appliance from the power supply.
2. This component is easy to spot, as it’s attached to the outer cabinet.
3. Depending on the model of your microwave, you’ll need to remove either one part or the entire cabinet of the appliance to reach the damper.
4. Make sure to thoroughly inspect the damper assembly to see if there are any visible signs of damage, such as cracks.
5. In case you see any visible damage, you should order a replacement damper assembly.

5. Faulty Fan Motor

One of the reasons why you might be experiencing problems with your microwave fan is due to a faulty fan motor. To check whether this component is causing the issue, you will need to remove it from the appliance and check it for continuity. The motor is located at the back of the appliance, near the top.

Inspect Fan Motor

Before you do anything, make sure to first unplug your microwave. After you do this, you can get started with testing the fan motor for continuity with a multimeter. Here’s how you can do it:

1. First, remove the cover of the fan motor.
2. Now remove the entire fan motor, so you can test it.
3. Grab a multimeter and set it to Rx1.
4. Connect the leads of the multimeter to the terminals of the fan motor and test it for continuity.
5. In case you get a reading of 0, it means that the fan motor is working properly.
6. In the event that you get any other reading, you’ll need to order a replacement fan motor.

You can find more info on how to test a microwave fan motor in the video below.

Checking of microwave oven cooling fan motor using multimeter

6. Faulty Thermostat

The thermostat in your microwave is directly tied to the fan. It gives a signal to the fan when it should turn off or on depending on the temperature in your microwave oven. Nevertheless, it might stop working properly after a certain amount of time and not send the correct signals anymore. In case your microwave fan won’t turn off, you should check whether the thermostat is working properly.

Replace Thermostat

In case you’re continuously experiencing issues with the microwave fan, you might need to replace the thermostat. Here’s how you can do it:

1. Start off by unplugging the microwave.
2. Now open the door of the microwave oven and remove the screws that secure the grille.
3. Remove the grill and unscrew the screws that secure the control panel as well as the screw behind the panel.
4. Detach the panel and you’ll see the thermostat.
5. Remove the mounting screw and the wires from the component.
6. Install the new thermostat, replace the mounting screw, attach the wires, and reassemble all of the other components.

You can find a more detailed guide on how to replace a microwave thermostat in the video below.

GE Microwave Vent Thermostat Replacement #WB27X709

7. Failed Control Board

It’s not often that you’ll experience problems with the microwave control board. But if you’ve inspected every other component that could cause the fan to run continuously and everything seems to be working fine, you should check the control board.

It’s not that hard to determine whether a microwave control board is working properly. For instance, you can easily know that this component is faulty if the buttons on the panel don’t work. This simply means that electrical signals won’t reach the board.

Replace Control Board

As with any tests and replacements involving microwave components, you’ll have to start by unplugging the appliance. Only after you do this step can you get to replace the control board.

1. To access the control board, you will first need to remove the screws securing the grille above the microwave door.
2. Now remove the grille and you’ll see mounting screws that secure the control board.
3. Take a photo of the wires attached to the control board to know how to connect them afterward.
4. Gently disconnect the wires from the faulty control board.
5. Grab the new control board you ordered for your microwave oven and attach the wires accordingly.
6. Reassemble all of the parts you removed during the process, and your new microwave control board should be working properly now.

How Do You Reset The Fan On A Microwave

There are multiple ways to reset the microwave fan. In case it won’t stop running and you’re curious about what the problem is, you should use one of the following methods to turn off the fan.

Switch Off the Fan Manually

The exact way to switch off the fan manually from the settings will vary slightly depending on the manufacturer of your microwave and the model. In essence, all you’ll have to do is press the “Options” or the “Control Setup” button on the appliance and then search for a “Vent Fan” option. Once you find it, press the button to switch it off. Give it 30 minutes and then manually turn on the fan.

Clean Your Microwave

Sometimes, the only thing you’ll need to do to put an end to problems with your microwave fan is clean the appliance. It may sound simple, but it’s often the easy fix needed to get everything working normally again. In case you don’t clean your microwave often, it will prevent the air vents from working properly, which causes the fan to work overtime to cool down the appliance.

Unplug the Microwave

You should use this method only if you can’t get the microwave fan to reset using the two methods mentioned above. This is a simple fix that often does the trick. After you unplug the microwave, give it about half an hour before you connect it to the main power supply. This will both reset the fan and give your microwave time to cool down.

Microwave Brands Affected with Fan Issues

You might experience issues with the microwave fan in models made by many different manufacturers. This includes microwaves made by Bosch, Kenmore, Samsung, GE, Whirlpool, Fridgeair, Maytag, and LG.

FAQs Microwave Fan Won’t Switch Off