Yep, Jim is right. You are forced to use your Air Con to make the interior right as far as temp. What I do in my Mach1 is turn it to low aircon (right where the blue starts to turn to red) and open the windows in nice weather. You can also turn your aircon completely off and just use the open windows, but you are not going to get cool outside fresh air through the aircon system. That's one of the many reasons why I love to drive my 65 during the Fall and Spring months as opposed to the Mach.