TC auto AC question

Have a 2003 TC with the driver/passenger automatic AC unit. When set at a temp of about 72 on one side and 75 on the other, the unit blows REALLY cold air both sides, seems no differential. Have to crank it up to maybe 80/84 before it seems to work properly. Where does it sense the AC temp ? Can it somehow be set to be more accurate at lower levels. I think it is probably working OK in the differencial mode, but the temp sensor is reading too low ? ? Thanks ! Zork