Why Won’t My AC Fan Turn Off?

Your AC fan should turn on and off with the rest of your heating and cooling system. It’s normal for the fan to kick on a couple of minutes before heating starts or to stay on for a couple of minutes after cooling stops, but your fan shouldn’t run for hours on its own.

Common causes for fans not turning off when they should include faulty thermostats, bad wiring, and stuck relays.

These problems are not easy DIY repairs and should be left to an HVAC professional.

Check Your Thermostat

Your blower fan works together with your heating and cooling units, but it’s really a separate electrical system.

Your blower fan is what pulls the uncomfortable air out of your home, sends it through the air conditioner or furnace, and then distributes it back into your home. The thermostat is what tells these separate systems to work together.

The fan in your AC system can run separately from the cooling component of your AC. These two parts work together to cool your home, but don’t always turn on and off at the same time.

In normal operation, when your thermostat is set to “auto,” it will tell the blower fan plus the heating or cooling components to turn on and off at the same time when the desired temperature is reached.

The only other time your blower fan should be running on its own is if you’ve flipped the thermostat switch to “on” to temporarily run your blower fan for increased air circulation.

Check Your Thermostat

However, regardless of whether the cooling component of your AC is on or not. To see if this is your issue, check your thermostat and ensure that it’s set to AUTO instead of ON. If your thermostat FAN is set to AUTO but your system is still running when “turned off,” you are likely experiencing one of the below issues.

When your thermostat isn’t working properly, it may not be able to accurately gauge the temperature of the room, which can cause your AC to run constantly or to turn on when it should be off. If this is your issue, you’ll need to contact an HVAC technician to check out your thermostat and repair or replace it.

To see if this is your issue, turn your thermostat up 5-10 degrees and see if your AC shuts off. If so, this is likely the problem and is due to the fact that your AC system is too small for your home. An undersized AC system will struggle to cool your home when temperatures are high, resulting in a system that runs continuously.

Weather Extremes Cause Havoc With Your HVAC

If it’s extremely hot or cold outside, your HVAC system may not be powerful enough to reach your desired temperature.

In that case, it will keep running until the outside weather improves. If both the fan and either the cooling or heating system are running unexpectedly, you may have a faulty thermostat. If only the fan is running, there may be a broken relay switch preventing the settings you enter on the thermostat from being sent to the fan.

To prevent future AC and heating issues, it’s critical to schedule regular tune-ups with Trust Heating and Air for your HVAC system. Small problems often build up over time, so you may not even realize you’re wasting energy and money each month.

Furthermore, once the stress on your system becomes too much, you may find yourself with no heating or cooling at all.

Weird Sounds Are Not a Good Sign

Along the same lines, if you notice any unusual scraping or whining sounds coming from your HVAC system, you should get them checked out as soon as possible. An early repair is often easier and cheaper than a late repair, which could end up forcing you to replace your entire system.

Trying to fix electrical problems on your own could cause more damage or even create a fire hazard. For safe and fast repair, contact Trust Heating and Air. We offer emergency repairs, routine furnace and AC services, and maintenance plans.

Check The Weather First

Before you assume there’s an issue and call a professional, check the weather. If it’s extremely hot outside, your AC may be running longer or more often than usual to compensate for the temperature outside. This is completely normal.

Is Your HVAC Unit Large Enough for Your Home?

If your AC system is too small for your home, you may need to consider replacing it. Relays open and close electrical circuits to various parts of your AC system, most notably, the fan.

Over time, relay switches can become stuck or damaged, preventing the thermostat from communicating with the fan.

So even if you turn your AC off, the fan will continue to run. This is a fix an experienced technician will need to make. If you suspect you have a stuck or damaged relay switch, we would advise you to reach out to your local HVAC company.

If your AC system short circuits, the commands you enter at your thermostat likely aren’t getting passed onto your system.

Contact us at Trust right away, so we can fix the problem.