February 2, 2023
HVAC Service in Sacramento, CA

Your home’s HVAC system has many individual components. Each component works together to perform the heating and cooling you love. The HVAC fan is just one of those parts, but you may notice that it runs longer than the others.

Don’t worry, it’s normal for your HVAC fan to run a bit both before and after running air conditioning. However, when the fan continues to run for hours on its own, you have a problem. Keep reading to find troubleshooting and advice on a runaway HVAC fan.


Your HVAC blower fan will run with both heating and cooling. The fan is what circulates air into your HVAC system. It will send it through the heater or air conditioner before distributing it back throughout your home. The system thermostat is what directs these different systems to work in conjunction with one another.

Normal operations would have your thermostat set to “auto” mode. In auto mode, either the heating or cooling works with your fan to reach the correct temperature. Many systems might have blower fans run for an extra moment or two. This is to get air flowing.

The blower fan will also run by itself when the thermostat is used just for air circulation. Just look at your thermostat to see what it says. If it’s “on,” then just change it to see if it returns to normal operation. If it’s not the thermostat settings, then it’s possible you have one of the real problems we address below.


One possibility is that the system is functional but just doesn’t have enough power. When the temperatures outside are very hot or cold, then your home’s HVAC system can be overwhelmed.

If the unit is undersized, then it’s not going to be up to the workload required of it right now. It might also be struggling because it’s in need of maintenance. In these cases, it’s likely to continue running until such time that the outside weather gets better.


If you set the thermostat to “auto” and it doesn’t run as it should, It might be the thermostat itself.

You might also have a broken relay switch that is keeping your thermostat settings from being communicated to the fan. Also, there might be a short circuit or wiring problem somewhere that is keeping your system from communicating correctly.


Hopefully, your HVAC system has a relatively simple issue affecting the blower fan. A qualified technician might be able to identify the problem and rectify it quickly. Then, you can get back to a quiet, comfortable life inside your home.

If the problem ends up being a symptom of major failures in your system, you may be considering a replacement. Your technician will have options for you, but the decision is eventually up to you.

One thing your technician might do is use a formula that’s very popular across the entire industry. Take the cost of potential repairs, and then multiply that number by how many years old your system is. If the number you come up with is greater than $5,000, then you should strongly consider replacing it.

Air conditioners may run for up to a decade with the right maintenance. A good furnace may last 15 years or more. Always keep safety in mind, however. If your system presents a possible hazard to your home, then a replacement is absolutely the right move.

There are two big potential safety issues to consider above all else. The first is the possibility of carbon monoxide poisoning, and the second is the chance of a fire hazard. Never put up with either being a possibility for your home.

If you’ve had your system for a long time, there might be new technologies that you aren’t taking advantage of. Digital systems that replace analog models are considerably more efficient. You might enjoy some serious energy savings on your utility bills. The right repair might also bring your power bill down by keeping your blower fan from working too hard.


Even if your HVAC system is working fine, you should probably get maintenance visits twice a year. Spring and fall are great times to do this. Your system usually isn’t working as hard, and there might be more professionals available.

Regular maintenance calls can prevent future heating or AC issues and correct anything that’s a minor issue now. Without professional service, your system will get stressed out over time and eventually fail. This is likely to happen when it’s really hot or cold outside. To make matters worse, there will be fewer professionals available during these peak temperatures.

Listen for whining and scraping sounds, and take notice of a fan that keeps on running. Early repairs usually prove faster and more affordable than later circumstances that might involve an entire system replacement.


If you’re dealing with an HVAC Fan that won’t stop running, consider giving Gallagher’s plumbing, heating, and air a call. Our experts will draw upon over 30 years of professional experience to make sure your HVAC is running optimally.

company icon