when running your ac you can set it to recirculate and it will make the air coming out of the vents a little coolerI am not sure which mode to use. Some people say the circulation mode and some people say the A.C.
see normally your ac is cooling the out side air which is lets say 80 degrees
when this 80 degree air flow over the evaporator core it can only drop the temperature so much
when on recirculate the cooler air already in your car is passed through the evap core and that allows it to cool that air even more