When the blower fan of a furnace keeps running continuously it is a sign of a problem which should be taken care of as soon as possible by heating repair services. However, you should know the reasons why it happens and the things that you can do to fix it.
Check The Thermostat Settings
The furnace keeps running issues could be because of incorrect thermostat settings. Therefore, check the settings of your thermostat first when you identify that the furnace is running without cycling off.
You should focus on two things when checking the thermostat settings. Firstly, the thermostat fan settings should be on AUTO. If the setting is at ON, switch it to AUTO because the ON button forces the furnace to keep blowing air until it is switched back to AUTO. Change the settings and wait for a few minutes to check if the furnace cycles off.
The second thing to check is the temperature settings. Sometimes, a furnace doesn’t turn off because the set temperature is too high and the weather outside is too cold so the furnace keeps heating and blowing hot air continuously to reach that temperature. If the temperature is too high, set it to low and notice any changes.
Ensure The Fan Limit Switch Is Not On Manual Mode
The fan limit switch controls the functioning of the furnace blower. You can find it inside the panel cover of your furnace.
When the fan limit switch is set correctly and working in optimum condition, it turns on the blower a few minutes after the thermostat sends the signal for heat and turns off the fan a few minutes after the heat cycle ends.
So, check the fan limit set and make sure it’s not on the manual settings because it will overall the thermostat settings and make the blower run continuously. You can check it yourself if you have knowledge of the furnace you have. See inside the furnace’s hood and you’ll notice a white button. It is the fan limit switch.
The button should not be pushed in because it means the manual mode is on. Push the switch out to switch it to the AUTO mode. If not sure, simply try to push the button out and check the furnace.
If you can’t find the fan limit switch, let a furnace technician check this for you and also change the settings if it is in manual mode.
Faulty Fan Limit Switch
A malfunctioning fan limit switch can also be the cause of the blower fan running all the time. You would have to replace the fan limit switch as soon as possible with an expert to fix the problem. This will also ensure an inspection from the expert who will be able to tell you more about the issues and also spot other problems if any.
Other signs of a faulty fan limit switch:
- The furnace starts blowing cool air
- The furnace begins short cycling (turns on and off in short intervals)
Thermostat Wiring Problems
If the wires in the thermostats short out they won’t be able to send signals to the furnace when to stop and start. This can keep the furnace running without stopping. You should inspect the thermostat and get it repaired or replaced for fixing the problem.
Fan Limit Switch Wiring Issues
Similar to the thermostat wiring, if the fan limit switch wiring is shot, it will stop the fan limit switch’s control over the fan. So, the fan may run continuously. You should perform repairs or replacement of the fan limit switch.
Furnaces Require Regular Maintenance
If you don’t want your furnace to break down in the middle of the night when it’s freezing outside, ensure regular maintenance. Replace the air filters, clean the air ducts, change the thermostat batteries, and follow the user manual for best results.
When a furnace doesn’t stop and keeps running all the time, the causes of the problem are the thermostat or the fan limit switch. An inspection can show if you only need to change their settings or if they are faulty and require replacement. Make sure to hire furnace repair services DC for fixing your furnace problems.