The air cond has been switching from normal air out the vents to the defrost and then after you are sweating it goes back to normal? Its a 95 Eldorado. I have the factory manuals for a 96 (missed out on the bid for the 95)and now I understand why it cost so much for the dealer to fix something. The factory does not give them a good check source. Hope some one has a good start point to check! Before the wife takes my truck!!
Thanks
Duke

it sounds like one of two things. either the switch is going bad, which is the cheapest and easiest fix i would think, or it is someting in the blower box, like a bad blend door actuator.