How to Stop a Furnace Fan from Running Continuously How to Stop a Furnace Fan from Running Continuously

What You'll Need
New thermostat

During certain seasons of the year when you find it necessary to run your AC or furnace, you may find that your furnace fan is running continuously. Typically, this is caused by an incorrect setting on your thermostat, a defective thermostat, or by a furnace limit switch that needs to be adjusted or replaced.

Step 1 – Check Your Thermostat

Check the settings on you thermostat. If the fan setting is turned to "ON," switch the setting to the "OFF" position or the "AUTO" position. If the switch is already turned to either if these last two settings, check your AC/Heat register to see if hot or cold air is coming from the vent. If you feel room temperature air, the problem could be with the limit switch.

Step 2 – Check Your Limit Switch Settings

Find your AC system user’s guide and follow the directions you find there for resetting the switch's pointers you'll find on the limit control's "Fan" side. If you are able to see these pointers, check to see that the lower one is set at approximately 90 degrees F. The higher one should be at approximately 115 degrees F.

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