ac not working '97 900s

Probable causes here could be the magnetic clutch, pressure switch and air blend door stuck in the heat position bring it in and have it further checked-

did you check the a/c condensor pressure switch ,if bad you will not get compressor to turn on at all ,note you can wire compressor power straight for a very very short time just to check compressor clutch function ,note only do this for testing ,also note if left like that you will blow compressor up ,so only do it for a short time for testing ,if clutch works then replace condensor pressure switch and that should work for you ,but before all that make sure to check fuses & relays for proper function ,good luck.