Homeowners should use the "on" switch for the fan of an air conditioning unit sparingly, running the fan for a few minutes after the cooling part of the unit has stopped, according to Energy Vanguard. Using the "auto" option for the fan is a better choice.
Most air conditioner units have buttons labeled "fan" or "auto." Some air conditioner technicians recommend putting the air conditioner's fan setting permanently to "on" to distribute cool air around the home evenly, but this strategy can backfire and add more humidity to the home, according to Energy Vanguard. Instead, homeowners should choose the "auto" option, or if homeowners choose to run the fan, they should do it for just a few minutes after the cooling part of the unit shuts off.
Air conditioning units have two main components, one that cools the air, and another that distributes the cooled air around the house. As the air is cooled, it also has moisture stripped from the air that condenses on the cold evaporator coil. An air conditioning unit that shuts off the cooling part after a short run may have water sitting on the coil, and when the fan is run after the cooling part shuts off, the water on the coil may evaporate and go right back into the air, claims Energy Vanguard. When this water goes back into the air, it raises the humidity level and can make a home feel uncomfortable even after it has been cooled off by several degrees.