Why Will the Blower on My Furnace Not Go Off?

Temperature Control Switch

• The temperature control switch in your furnace is made to turn your furnace on and off depending on the current heat level in the home. If it won’t shut off at all, there is a good chance the problem is with this switch. Some furnaces have an adjustable fan control, but the temperature control switch is usually nonadjustable and must be replaced entirely if the problem persists.

Thermostat Setting

• When your furnace will not shut off at all, it could be simple user error. Your thermostat is an easily accessible control that allows you to choose what temperature you want your home to remain near. If you have set your thermostat to a very high temperature, then the furnace may have to stay on to attempt to reach that level. This should be an obvious problem if the home is getting hot. All you need to do is lower the thermostat setting and see if the system shuts off. It may take it a few minutes to respond, but the system should shut down once it realizes the desired temperature has been reached.

It’s Very Cold

• Your climate may have something to do with the furnace’s constant running. If you live in a place where the outside temperature is extremely cold, the furnace may be simply doing its job. This is especially true if your system is undersized. The furnace has to run continually to try and reach the level of warmth you desire. It may not be able to reach your preferred temperature because of lack of output BTU power or if the home is losing heat because the weather is frigid.

Fan Setting

• Your furnace is likely equipped with a fan setting switch that allows you to keep the blower running at all times even if the burners or heating elements are not running. This will sound like the furnace is working all the time because it blows whether it is producing heat or not. This setting, while using more energy, allows users to maintain more even temperatures in the home. Switching the fan setting to “off” or “auto” should allow the system to shut off from time to time, assuming there isn’t another problem.