Why Does My Microwave Fan Come on by Itself? Causes and Fixes

Why Does My Microwave Fan Come on by Itself? Causes and Fixes

Have you ever heard a loud humming sound coming from your microwave, even when it isn’t in use? Many models of microwaves have a built-in fan that can sometimes activate automatically. This is usually due to a malfunction in the system and should be investigated by a professional technician if it becomes too annoying.

In this article, we’ll explain why this happens and how to go about fixing it. You’ll soon be able to take control of your microwave fan again!

What Causes a Microwave Fan to Come On By Itself?

Many microwaves have airflow systems in place to help keep their electronics cool and prevent overheating. These fans are designed to come on and off as needed, often turning on when the microwave is active or has been on for a while. However, if the fan appears to be running without any activity or recently stopped running suddenly, this may be an indication of a problem.

The reasons why your microwave fan may turn itself on or off vary, with few clear answers, so it’s best to contact a professional if you’re unsure of what might be causing the issue. Common causes for the fan turning on include:

  • Excessive cooking time – If your dish needs more time than usual, consider changing the cooking setting or stirring it more often.
  • Dirty filters – Dust and dirt can reduce airflow which can cause overheating problems. Make sure your filter is replaced regularly and kept clean.
  • Faulty electronics – This could be caused by anything from worn out capacitors to loose connections stemming from age and wear and tear of elements inside the microwave.

In any case, never attempt to open up your microwave without professional assistance as this could cause a hazardous malfunctioning electricity related situation inside your appliance. The best course of action is always to call for professional help if you are uncertain about what could potentially be causing the issue.

Common Reasons for a Microwave Fan to Turn On

There are a few different reasons why your microwave’s fan may randomly turn on. Typically, it’s a sign of an issue with the cooling system, so you should address any problem as soon as possible to avoid potential hazards.

Related Post:  How to Reheat Hash Browns: Tips for Crispy and Delicious Results

Here are a few common causes of this issue:

  1. Blockage in the air filter– If there is something blocking the air flow between the fan and the interior of the microwave, like dust or debris, this can cause your fan to come on unexpectedly. Inspect the filter and replace if necessary.
  2. Malfunctioning temperature sensor– The temperature sensor inside your microwave is responsible for regulating heat levels within its interior. If this fails or is defective it will cause excessive heat inside your microwave, which in turn can cause your fan to come on due to overheating.
  3. Faulty door switch– The door switch on a microwave operates by connecting two terminals when it senses that the door has been opened or closed. If this switch fails it can wrongfully indicate that the door has been opened, causing the fan to turn on even when no one is using the oven.
  4. Overloaded circuit– If a single outlet is supplying power to multiple appliances at once, additional strain can be put on it which could potentially cause issues with appliances connected via that same outlet—including possibly triggering regular activation of your outlets fan while not in use.

How to Diagnose and Fix a Microwave Fan That Comes On By Itself

Having a microwave fan come on by itself can be not only an annoyance, but can be a concern if the fan doesn’t actually shut off. This issue can occur when the fan is on its last legs, or when the microwave is not installed properly. In any case, there are some steps you can take to figure out what’s going on and get your fan running smoothly again.

  1. Check the installation of your microwave to make sure that it’s installing correctly and that it’s secure. If there are gaps between where the microwave meets with the cabinetry, then it could cause airflow issues which would result in the fan randomly turning on and off. Make sure to seal up all gaps with caulk or weather stripping, depending on what material you’re using in your kitchen space.
  2. Inspect inside your microwave for signs of abnormal wear or tear such as burning smells, rusting parts etc., as these could all be tell-tale signs that something isn’t working correctly and needs immediate attention. As faulty wiring or defective parts could both lead to a malfunctioning fan, examine those interior components carefully to see if they need replacing.
  3. If all else fails and none of these steps have had any effect in stopping your fan from coming on randomly then consider calling an appliance repair service for assistance as some microwaves require specialized supplies for fixing fans due to their unique size or shape requirements. With detailed inspection and proper installation techniques from an expert technician, hopefully you’ll find yourself back enjoying delicious foods cooked thanks to a fully-functional Microwave Fan!

Possible Causes and for the Fan to Turn On

If the fan in your microwave suddenly turns on by itself, it can be alarming and confusing. But with a few easy checks, you can determine what is causing the fan to initiate and address the underlying issue to keep your microwave running safely.

Related Post:  How to Silence Your Frigidaire Microwave?

Common causes of erratic fan behavior include:

  • Inadequate ventilation,
  • faulty component parts,
  • incorrect wiring, and
  • a blocked air path.

If the fan is required to keep objects outside of the microwave cool or to limit its internal temperature, it should be able to run promptly when needed – otherwise, it’s likely that something needs adjusting.

How to Prevent a Microwave Fan From Coming On By Itself

If you notice that the fan in your microwave is coming on for no apparent reason, it is likely due to an issue with the temperature sensor. The temperature sensor measures the internal temperature of the microwave and triggers the fan as needed to cool it down. If there is an issue with this sensor, it can cause the fan to come on spontaneously. Fortunately, there are some steps you can take to prevent a microwave fan from coming on by itself.

  • Try cleaning out any dust or dirt that has accumulated inside your microwave. This can help ensure proper airflow and temperature regulation.
  • Try recalibrating your microwave’s temperature sensor by unplugging the appliance and pressing its “Sensor” button three times. Then plug it back in and press its “Start” button once to complete the reset process.
  • Check for any damaged components inside your microwave – particularly wiring or wiring connectors – and replace them if necessary.
  • In some cases, a faulty heating element may be causing excessive heat build-up within the appliance and triggering the fan prematurely; these elements should also be replaced if necessary.
  • Finally, avoid pushing any buttons while food is cooking as this can interfere with normal operation of its sensors and other components.
Related Post:  Cooking Tilapia in the Microwave: A Quick and Easy Guide

By following these steps, you should be able to identify and address any issues that could prevent a microwave fan from coming on by itself in future.


It is normal for the fan in your microwave to come on when the door is opened, during cook/defrost cycles and after a self-cleaning cycle is complete. In most cases, if your microwave fan runs all the time or starts running by itself unexpectedly, this points to a problem within the microwave that requires a professional repair.

If you experience this issue, it’s recommended to contact an appliance technician to diagnose the issue with your particular model. In rare cases, you may need to replace the control board or other components of the appliance:

  • Control board
  • Other components


When the fan on your microwave turns on by itself, it’s likely a sign that the device needs a bit of attention. There are some frequently asked questions which can help you diagnose why the fan is running:

  1. Is the fan running while I’m using my microwave? – If so, this could be an indication that your microwave needs some airflow to help it function properly and keep its internal temperature regulated.
  2. Is there any smoke or odors coming from the area around the fan? – If there are signs of burning or discolored areas near the fan, this could be a sign that something inside the appliance is overheating and needs to be inspected immediately by a professional.
  3. Is my appliance within warranty period? – If so, contact your manufacturer and arrange for service as soon as possible as most warranties cover labor as well as parts replacements if necessary.
  4. Are there any mechanical noises coming from inside my microwave when it’s running?- Abnormal noises like grinding or clunking can indicate trouble with motor bearings or other internal components which will require servicing by a qualified technician in order for them to be repaired safely and quickly.

Similar Posts