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9 Reasons Why Microwave Fans Won’t Turn Off (& Fixes)

Microwave Fan

Yummy Pizza!

The only thing that comes to mind for heating a yummy pizza for midnight snacking is a microwave oven. It is a convenient device that provides warm food and drinks within a few minutes.

However, the device can malfunction and start acting unusually. The microwave has an exhaust fan that helps regulate the temperature of the device, but sometimes it doesn’t turn off, making you look for the reasons and quick fixes.


The microwave fan can run continuously due to the following reasons:

  • Overusing the appliance.
  • Malfunction in the control board.
  • A thermostat failure.

Are you worried about your microwave oven fan? Read further as we uncover why your oven fan won’t turn off and quick ways to fix it.

9 Reasons Why Microwave Oven Fans Won’t Turn Off & Quick Fixes

Nobody likes the unwanted sound of a microwave fan that never turns off. It is annoying and worrisome as it indicates some fault in your device.

Here are a few reasons why it won’t stop and easy ways to fix it:

1. Overusing the Appliance

Overusing The Appliance

Microwaves have a special “Faraday shield” that keeps the radiation inside the cooking area. It also helps in regulating the temperature of the device.

However, prolonged use of the microwave can increase the temperature and heat the device.

Once the thermostat inside the microwave detects a high temperature, it signals the exhaust fan to turn on. Even when you turn off the device, the fan won’t stop running until the cooking chamber’s temperature is lowered.

Quick Fix

The easiest way to avoid overheating your microwave is to use it wisely. Avoid using it for longer, and at least give a break of 10-15 minutes before heating another food item.

2. Malfunction in Control Board

Control Board

The control board is like the brain of the microwave oven. When you press a button on the exterior panel, it transfers the signal to the control board that performs the required action.

However, if your control board is faulty, it won’t signal the fan about turning on or off respectively.

Quick Fix

The first thing is to clean the control board as accumulated debris and grease can damage its working:

  • Thoroughly clean the exterior control panel by rubbing alcohol to clear out any sign of grease on the outside.
  • Remove the control panel covering and assess the interior and cable connectors. Clean the parts thoroughly and place everything back.

If your microwave still shows the same error even after cleaning the control panel, it is better to get an expert’s advice and replace it.

3. Inappropriate Ambient Temperature

Inappropriate Ambient Temperature

Placing your microwave at a high ambient temperature, like in a kitchen, can cause it to malfunction and heat up quickly.

Even when the appliance is not working, the thermostat will repeatedly turn the exhaust fan on to regulate the device’s temperature, making the fan work for longer.

Quick Fix

The best solution is to keep your microwave oven in a cool place away from stoves or other heat sources. It will help the thermostat assess the accurate temperature and work accordingly.

4. Clogged Air Filters

Clogged Air Filters

The microwave oven has air filters that clear the fumes and steam coming from the food before letting the air go into our homes. It is a safety feature that purifies the air. However, the filters can clog after prolonged use.

Quick Fix

  • Locate air filters in your microwave oven using the appliance’s user manual.
  • Clean the filters with warm water and soap and place them back.
  • If you see any damage in the filters, immediately replace them.

5. Lack of Air Circulation

Air Circulation

Your microwave has vents that help it expel the warm air while heating your food. However, if your microwave vents are blocked from any side, it can heat the device resulting in the thermostat kicking in and turning on the exhaust fan.

Quick Fix

It is advisable to keep your microwave away from the walls to ensure maximum air circulation.

Always ensure you have placed nothing on the appliance, as it can hinder ventilation.

6. Thermostat Failure

Thermostat Failure

The thermostat in your microwave oven signals the control board to turn on the fan once the microwave oven starts getting hot. It helps maintain the device’s temperature and prevent it from heating up.

However, if the thermostat malfunctions, it won’t indicate when to turn the exhaust fan off to the control panel.

Quick Fix

  • You can locate the thermostat of the microwave with the help of the user manual.
  • Use a multimeter to check the correct flow of current.
  • If you suspect damage, ask a professional for a replacement.

7. Blocked Grease Filter

Blocked Grease Filter

Your microwave also has a grease filter that accumulates oil and grease from your food as it heats up. Like an air filter, the fat builds up and clogs the filter if it’s not cleaned regularly.

A clogged grease filter can overheat the appliance resulting in turning on the exhaust fan.

Quick Fix

  • The grease filter is located at the bottom of the microwave oven.
  • Take the filter out and thoroughly clean it with warm water to remove the grease.
  • Once it is cleared, deeply wash it with soapy water and place it back.

8. Faulty Fan Motor

Faulty Fan Motor

The exhaust fan requires a motor to work appropriately. If the fan motor malfunctions, it won’t be able to turn on or off correctly, resulting in a faulty exhaust fan.

Quick Fix

You require a professional’s help to assess the motor and get it replaced if needed. However, repairing a faulty motor is not cost-effective; getting a new one is better.

9. Defective Damper Assembly

Defective Damper Assembly

The primary purpose of a damper assembly is to direct the airflow through the microwave and ensure that the air correctly flows through the vent duct.

If the damper assembly malfunctions, the air won’t pass correctly through the vents resulting in the appliance heating up.

Quick Fix

You can inspect the damper assembly and manually unstuck it if it’s jammed. However, in case of structural damage, it is better to replace it.


Dealing with a microwave fan that won’t turn off is nothing less than a pain in the neck. The constant annoying noise and heating up of your appliance can also cause severe damage.

You can fix the exhaust fan issue with DIY quick fixes discussed above. However, if you are unsure about the solution, call a professional to get help.

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