Cadillac STS

I have a 2002 Cadillac Seville STS with 48,500 miles. I have an issue with hot air coming from the floor when I open the window or sunroof. The climate control is off and I still get hot air what ever the outside temp is. I also took some advise from a friend that has a GM model and he just turns his climate control down to 60 degrees to stop it. I did this on a day that it was 75 degrees and still got hot air. I have taken it to the dealer several times and gotten different explanations. The latest was; " That is a design change from 1998 and you have to live with it" Please tell me if this in fact true.
April 23, 2007.

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