There’s one thermostat setting that can cause some confusion: the “on” and “auto” setting for the HVAC system’s fan.
Fan On vs. Auto: Learn Which Thermostat Setting You Should Use
When you’re setting your thermostat, you have the choice to run the fan in the HVAC system. You can have it constantly running by choosing the “on” setting, or running it only during the heating or cooling cycle with the “auto” setting. Both choices have advantages and disadvantages, depending on the circumstances.