Inverter Fan Running Continuously: Best Complete Answer

Like a laptop or other heat-generating device, a power inverter uses a fan to keep itself cool. And without that fan, that device would overheat and cause a shutdown. 

But what if your inverter fan is running continuously? What is the problem?

Common causes of inverter fans running continuously include poor ventilation and overloading. This post will review the common causes and solutions to the fan always running, including:

  • Ambient Temperature
  • Ventilation 
  • Overload
  • Weak Battery 

When you hear the cooling fan always run, it can be annoying and make you wonder what the problem is.  Luckily, there are a few quick steps to see what is causing this fan to run constantly. 

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When you look at a power inverter, it is plain to see that the main concerns for the function are temperature and heat. Engineers have thought diligently about how to remove the generated hot air.

Just looking at the inverter, you will see vents, aluminum housing, and, in many cases, some with fins. This housing and fin design’s main function is to help eliminate the generated heat. And to no surprise, the fan mode function is to push out that hot air to keep the power inverter cool. Keeping fan speed in mind and cooling.

Inverters designed to give off heat

Ambient Temperature

Once your inverter senses a higher temperature, the fan will automatically turn on. This auto feature varies from inverter to inverter, but generally, above 105 degrees Fahrenheit, the fan will turn on. So if it’s a summer day with an ambient temperature of 90 degrees, the internal thermostat won’t take much to turn on the fan. If your fan is continuously running and it’s a warm day, it could just be reaching the set temperature to try and cool down the inverter, even with a small electrical load. 


Another potential cause of the fan always running is ventilation around the inverter. Without proper ventilation, the inverter will trap any heat and cannot cool itself as designed. Many manufacturers recommend 1″ to 2″ of clear space or cold air around the inverter housing and the fan.

If you have any material on top of the inverter or something blocking the fan, it will continue to run constantly as the hot air and heat cannot escape the inverter.


If you have good airflow around your inverter and the ambient temperature is cool but still hear fan noise, it may be time to check the electrical load.

All inverters have a power rating, usually in watts. They can range from 500 watts to 5,000 watts. And to no surprise, each generates its fair amount of heat as power is used.

As the inverter converts dc battery power into ac power, more heat is generated as more watts are produced. More watts = More heat. If you are always hearing the fan motor, it could be that you are at a point where the power generates just enough heat to turn on the inverter fan.


Reduce the load on your inverter by turning off some appliances or lights on the inverter. As the load reduces, the heat should reduce. Give it a few minutes and see if the fan turns off as the inverter cools down by generating less heat.

Check that you have not exceeded the watts

Battery Power

If you have good ventilation and do not overload the inverter, battery power is the next possible cause of the fan always running.

Since the inverter uses dc power from the battery, it is critical to have a good battery to provide the voltage needed for your inverter to provide the 120 ac voltage. After all, the main purpose of the inverter is to make it feel like you have shore power when you are just using battery power.

Many inverter manufacturers recommend that the battery be fully charged up to 13.2 volts. And that the alarm will sound and the system will shut down when the battery voltage is below 10.5 volts.

When your battery is low voltage, the inverter works harder to make the needed ac voltage. That said, as the battery voltage goes down, the inverter works harder and creates more heat to produce that wanted 120-volt ac power.

For more information, visit the post on 12 volt batteries.


Check your battery voltage to see if it is low. A charged battery voltage should range from 13.3 Volts to 12V. Once you get below 12V, connect to a battery charger. Even though the inverter alarm will still work and not shut down until 10.5 volts, it still will work harder and generate more heat as it tries to keep up with the demand.

Another cause of the battery voltage issue is the wire connection. Any loose wiring can cause lower voltage and strain the inverter. Check the wire connection to the inverter and ensure it is tight and secure.  Also, check your connection at the battery terminal, as this can also be loose and need to be tightened. 

For more troubleshooting inverters, visit the post on inverter problems.

Final Thoughts

A power inverter is a luxury when you don’t have shore power. This little device gives you a complete ac system from your battery.  But, sometimes, you can hear that fan blade spinning continuously.  The most common causes of the fan always running are poor ventilation, unit overload, or battery power.