Why Is My Furnace Fan Running Continuously?

2 January 2020
 Categories: , Blog


The furnace blower is an important part of your heating system. In some cases, the furnace blower might operate continuously, but not provide any heat. When your thermostat is set to auto, the furnace blower should only run when your furnace is in the middle of a heating cycle. However, when the fan is running constantly regardless of whether the furnace is in a heating cycle or not, there is something wrong with the furnace.

Check the Thermostat

You do not want your furnace blower to run constantly because this will run up your energy bills and will also wear out your furnace. First, make sure that your thermostat is set correctly. If it is not set to auto, change the setting to auto so the furnace will stop running.

Inspect the Fan Limit Switch

Make sure that the fan limit switch is not in continuous mode. This is a white button in the lower-left corner that tells the switch whether it should operate manually or automatically. Reset the switch to auto so that the fan will operate properly. 

Lower the Thermostat

Consider lowering the thermostat. It's possible that you set the thermostat so high that the furnace is not able to keep your home as hot as the thermostat setting. As a result, it runs continuously as it tries to heat up your home. 

Open Vents in Heated Rooms

Make sure that all the vents in the rooms where you want heat are open. If the vents are closed, the furnace will not be able to direct heat to those rooms and will operate continuously as it tries to satisfy the demands of the thermostat.

Check the Control Board

The control board might be defective. The control board is responsible for sending a signal to the furnace to tell it to generate heat. However, the control board sometimes does not function properly and continuously sends the signal for the blower to keep operating. The control board might need to be replaced with a new one.

Call Heating Services

If you are not able to figure out why your furnace is running continuously, contact an HVAC contractor repair technician. A constantly running blower might seem like a nuisance, but it can also cost you a lot more money if you don't have the problem resolved promptly. You might have a bad limit switch or the thermostat wiring might need to be replaced.