Good Question. If I press Mode, nothing happens, it still says "auto". If I adjust the ***** for driver/passenger it responds appropriately,by adding heat or cold but it still just stays in auto. I think that the main problem is that it is always in Auto, and so it is always taking into account the air temp. I read the manual about the difference between manual and auto. Auto takes into account the air temp and makes adjustements based on your setting. Manual obviously leaves you in complete control but I just can not access manual.
I would think that it was the "manual" button itself, but let'* say that I turn on the air by turning the driver **** down to 60 degrees (full min temp), since I'm always in Auto, if the temp is hot enough, I will get cold are. I can manually adjust the fan setting while in auto. I usually press "AC" next, and then "Recirc". All three of these would then be displayed "Auto" "AC" and then the "Recirc" Led is on. If I press manual, "AC" is gone and "Recirc" Led is off, but I'm still in auto!