The HVAC system’s fan should always turn on and off with the rest of the system. The fan typically switches on a few minutes before heating begins or stays on a minute or two after cooling ends. That said, the fan shouldn’t be running for hours on its own.

Even if it is, this isn’t necessarily bad for the fan. What it does mean is that there are bigger problems you’ll need to address. If you’re wondering why your HVAC fan is constantly running, then read on.

How the fan should work

The blower fan works in concert with the heating and cooling units but is actually a separate electrical system. The furnace and air conditioner will heat and cool the air inside. The blower fan is responsible for pulling uncomfortable air out of the home, sending it to the furnace or air conditioner and then pumping the air back into the home.

The thermostat acts as the bridge between these two systems. When the thermostat is set to “auto,” it tells the blower fan plus either the cooling or heating elements to switch on or off at the same time once the temperature it’s set to is reached. For many systems, the blower fan runs a bit extra to get the air flowing to heat or cool the house. The only other reason for having the blower fan run on its own is if you’ve set the thermostat to “on” for increased air circulation.

Problems with furnace fan always running

If the blower fan is constantly running, then there are a few possibilities:

Extreme temperatures: When it’s extremely hot or cold outside, it may be that the HVAC system simply doesn’t have the power to reach the temperature you want it to. This may also occur if the system hasn’t been maintained or is undersized for the home. In this case, the blower fan will keep running until the outdoor temperature has improved.
Short circuit: It could be that there’s a short circuit or wiring problem that’s preventing the fan from shutting off.
Thermostat settings: One possibility is that your thermostat is set to “on” rather than “auto.” If it’s set to “auto,” the fan should eventually turn off.
Faulty thermostat: If both the fan and the cooling or heating system are running during times you don’t expect, then it’s possible that your thermostat is the problem.

What to do about an HVAC always running

Scheduling regular maintenance tune-ups with a qualified HVAC technician should stop this problem before it starts. If you notice any signs of problems like strange sounds coming from the unit, then call in the pros. It’s always easier and cheaper to take care of problems early rather than allow them to fester.

Is your furnace fan always running? Then call in the pros at Air Climate Control, Inc. We’re your go-to professional commercial HVAC repair service since 1991. Give us a call today to get a free quote and set up your first appointment.