Should your programmed thermostat be used with the fan switch set to on or off when using central air conditioning?

Your Thermostat Should Have Settings Of FAN- auto-off-on. If It Is This Way Set It To Auto, If Not Set It To On, It Should NOT Run All The Time Only When There Is A Demand Signal. Then Shut Off Until A/C Kicks On. If Your Condensor Unit ( Outside ) Is Running The Fan Should Be Also. When The Condensor(compressor ) Outside Unit Is Off Your Fan Should Be Also. If This Does`nt Help, Read Your Installation Instructions Over. If This Thermostat Is Not A New Installition. It Should Work As Above. HOPE THIS WILL HELP It doesn't matter, as far as the operation of the system is concerned. Some leave the fan switch "on", which means the blower will run constantly, believing this will provide a more uniform temperature throughout your home (and it really doesn't cost that much to operate the blower all the time). Others see no difference. I suggest you try it both ways, several days each way.