# Why Does My Furnace Keep Running?



## HVACPhilly (May 6, 2017)

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HVAC Philly FAQ; Why does my furnace keep running?*

Philadelphia has been hit hard by freezing temperatures. Residents in the greater Philadelphia, Bucks and Montgomery County, PA areas can certainly expect to be giving their furnaces a run for their money. However, when it seems as though your furnace is constantly running, without cycling off there may be a bigger issue than the frigid weather.

During the winter months your thermostat should be set to AUTO, and only be blowing when your furnace is in a heating cycle. A constant running “furnace” is actually your fan blowing air, whether or not your furnace is actually heating.

Now that we’ve established that it is NOT normal, we now need to figure out WHY? HVAC Philly, furnace repair experts in the greater Philadelphia area, offer some reasons as to why your furnace is constantly running. The top reasons are:

*A thermostat wire that has shorted*
*The fan limit switch has a shorted wire*
*The fan limit switch is on “manual override”*
*The fan setting on the thermostat is set wrong*

HVAC Philly will walk you through the possible issues, and help you with the correct steps to identify the problem. We will guide you to resolving the problem on your own and are here to provide professional assistance for furnace repair where professional help is necessary.

Your first step is to make sure that your thermostat is properly set. An improperly set thermostat can be the main reason for your furnace to continuously force heat into your home. These steps will help you to troubleshoot any thermostat issues you may have.

Try setting your thermostat to a lower temperature than the current room temperature. By doing this, you will shut the furnace down and will stop your thermostat from signaling for more heat. If your furnace was in the middle of a heating cycle, you will want to wait a few minutes for the blower fan to stop running.

After waiting 3 to 4 minutes, did the furnace fan stop blowing? If yes, that would indicate that you set your set thermostat temperature too high, making your furnace force heat continuously so it can reach that temperature.

An improperly winterized home can also cause your furnace to constantly blow heat as well, by hot air going out of the home and cold air coming in.

If, after adjusting your thermostat, you notice that your furnace continues working to heat your home without reaching the set temperature it is best to call in a professional to give a thorough inspection of your heating system and home to provide possible solutions.

Set your fan to AUTO not ON. A fan will continue to run if it is set to ON, despite whether or not your furnace is actually heating.

Setting your fan to ON will actually waste money as it forces the fan motor to run constantly.

After troubleshooting your thermostat the next step would be to troubleshoot fan limit switch problems
Right under your furnace hood, you will find your fan limit switch. The fan limit switch controls when your furnace fan turns on and off. Inside the switch is a probe that keeps track of the temperature of the burner assembly, it turns the fan on once the burners are hot and off once the burners cool down.

However, if your furnace fan does not stop blowing, here are 2 problems you might have with your furnace fan limit switch

Your fan limit switch may have been set to manual override
Your fan limit switch is faulty and may need to be rewired or replaced
To find out which of the above may be your issue, follow these steps listed below:

Find your fan limit switch located directly under the furnace hood, and check to see if the white knob is pressed in. If it is, that means your switch is set to manual override and would be always running.

You will want to then pull the white button out to reset your fan limit switch to AUTO. Doing this will ensure that the fan will automatically turn on when the furnace is heating and shut off once the need for heat stops.

If, when you check your fan limit switch, you find that the white knob was NOT pushed in, that would indicate that it was already set to AUTO and you would want to contact your local HVAC professional come in to inspect and perform any furnace repairs you may need to be done.



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