300sdl a/c blows only hot, have spent $$$$$$$

[moxwell]

hello all
My 1987 300sdl blows only HOT air out of the vents and to date I have had everything having anything to do with the a/c under the hood replaced. Still no cold air. My indy is very perplexed and he now wants to look under the dash. I was wondering if there are any recomendations as to what the problem could be. The buttons on the dash have no direct effect on the circulation of air as all the buttons seem to direct the air out of the same vents. HELP I live in deep south texas and I need to carry around a change of shirts to go to work as I am drenched by the time I get there. Any recomendations are greatly appreciated.