If the unit does not have the fan on/auto circuit, then you would have to make a control rewiring job to do it. It would not be recommended for a novice to try it.: What steps are required to enable fan on switch of my furnace thermostat? Is a : third wire required? Or isa jumper necessary? Any information would be deeply appreciated. I : have a 825 sq ft home with a 18,000 btu window air unit, would just like to have fan blower : circulate air through out home.: Sincerely, : Jeff Stoops