Why Your Furnace Fan Keeps Running Even With the Thermostat Off

Does your furnace fan run non-stop, whether the thermostat is on or off? Call Gladiator Services, Englewood Cliff’s trusted heating and air conditioning contractor, at 201-248-0952 and we’ll get your furnace running correctly today!

During the heating season, it’s important to know that you can rely on your furnace’s efficiency. The last thing your family needs in the middle of winter is a surprisingly high heating bill or, even worse, a faulty furnace. A common issue you might encounter is the furnace fan keeps running with the thermostat off, which is a problem that you should fix quickly. 

There are two main possibilities as to why your furnace fan is running all the time; the problem is often due to either an incorrect setting or faulty equipment somewhere in your HVAC system. Let’s go over six reasons your furnace fan won’t stop running and when to call an HVAC technician.

#1. Furnace Fan Set to “On”

Whether your furnace is brand new or 10 years old, it’s possible that a flipped switch is causing your furnace fan to keep blowing.

If you look at the fan setting on your furnace thermostat, you’ll usually see two modes: on or auto. The on mode will keep your furnace fan running at all times, even when your furnace is not generating heat. You might be able to fix the problem by flipping the setting to auto, which will make sure your furnace fan is automatically turning on or off when the furnace is heating.

#2. Fan Limit Switch Set to “Manual Override”

If you’ve determined that the furnace fan is set to auto but the fan is still blowing, open up your furnace and look for the fan limit switch. When functioning correctly, the fan limit switch controls when the furnace fan turns on and off by monitoring the temperature of the burner assembly. 

Check to see if the white button on the fan limit switch is pushed in. If so, your furnace is set to manual override, and the blower fan will run constantly. To fix this, pull the button out to reset the system to auto. Now your furnace fan should only run according to the temperature readings on the thermostat.

#3. Thermostat Too High

If all of the settings seem correct, you may have simply set your thermostat too high, and thus, the fan is running constantly, trying to get your home up to the desired temperature.

#4. Not Enough Insulation

When winter hits, you need to be confident that your home will be safe, warm, and comfortable for you and your family all season long. If you have an older home, it might be that your space is difficult for your furnace to heat due to gaps in insulation or improper insulation. An HVAC specialist can examine your home’s insulation and let you know if you need to supplement it or replace it.

#5. Broken Thermostat

Once you’ve checked all of your settings and turned down your heat to see if the fan stops at a cooler temperature, if your furnace fan keeps running with the thermostat off, it’s time to consider the other possible cause: faulty parts. A broken thermostat is often the culprit when it comes to your furnace fan blowing all the time. 

Your thermostat controls your entire HVAC system, using sensors that determine the ambient temperature in your home and turning your heating system on or off, depending on your settings. Whether you use a mechanical thermostat, a smart thermostat, or a combination of the two, it is a crucial component of your heating system that needs to be properly calibrated and working correctly to function. Try replacing the batteries or checking the wiring on your unit if your furnace fan is still running.

#6. Bad Wiring

After you have run through all of the possibilities of why your furnace fan keeps running even with the thermostat off, the final possibility is that there is faulty wiring somewhere in your HVAC system. This is a complicated issue that requires a qualified technician to diagnose and fix. If you suspect bad wiring is causing your fan to run, it is important to never try to fix it yourself. Call a professional immediately, as it is a dangerous issue, and you could injure yourself or damage your furnace even further. 

If you believe that faulty equipment is what is causing your furnace fan to run constantly, call the professionals at Gladiator Services. We’ll examine your furnace from the thermostat to the wiring and even your home’s insulation to identify the issue.

Call Gladiator Services for Help With a Running Furnace Fan

If you suspect an issue with your furnace fan, it’s never too early or too late to call an HVAC contractor to diagnose and repair it. Whether you don’t have time to fiddle around with your settings or simply would like a professional to diagnose the problem quickly, there’s no issue too big or small for Gladiator Services. 

In the event that you and your technician have run through all of the possible options and your furnace fan continues to blow, the issue might be that you have an old home that is difficult to heat. In this case, it’s best to have a professional discuss heating options for old houses with you. From updating your fireplace to sealing gaps or adding insulation, there are many ways to make sure your home is as comfortable as possible in the winter. 

Our qualified team of technicians at Gladiator Services can walk you through any furnace fan issue you might have, from optimizing your settings for efficiency to rewiring your furnace to considering new insulation or sealant options. We always arrive on time, and we’re so confident in our service that we offer a five-year labor warranty on every repair and installation. We know what to do if your furnace fan keeps running with the thermostat off, so call us today at 201-248-0952, and we’ll find your fix, fast!