If you notice that your fan is running all the time, you will want to know that this is not how your furnace should be operating. There are several problems that this can indicate. If your fan is set to auto, it should only run if your furnace is in the heating cycle. If it keeps running, this can be a sign that there is one of several problems.
There are some homeowners who deliberately choose to set their to run continuously. This is done to ensure that the air is always circulating and is helpful if your home has hot and cold spots. However, this decision can cost you hundreds of dollars a year in heating bills. You might even feel colder during the winter because you will feel the air blowing out of your vents even if the air temperature is similar to the space temperature.
Check the Fan Setting
Your fan might not be on the right setting. If you are not sure if the fan is on the right setting, you'll want to set the thermostat a few degrees lower to find out if it reaches the temperature set after a few minutes. If it does not, you should investigate whether your fan is working too hard to heat up your home. You can always try to remove layers of clothing if it's too warm, but you are still wasting money on heating.
Inspect the Manual Override
Your fan limit switch might be on manual override. The fan limit switch can be found inside the furnace panel cover and is near the upper right corner. The fan limit switch is designed to turn the fan on and off during the right moments. If it is not functioning properly, your furnace might overheat. One possibility is the fan limit switch is set to manual. Another possibility is that the fan limit switch is damaged and needs to be replaced.
There is a white button for the fan limit switch that will cause the fan to always be on. Make sure that it isn't pressed in. Otherwise, it will run continuously. Instead, you will want to set the switch to auto.
Contact a Furnace Repair Technician
If you have tried everything and your fan is still running, you will want to contact a furnace repair contractor to find out what is wrong. You might just have a bad thermostat wire and you might need to have the wire or your thermostat replaced.