'94 mustang air flow supply stuck
 

I have a '94. Recently, the vacuum control for the AC/Defrost/Vent/etc. will not switch over. It is stuck on Defrost, meaning the air flow always comes out the defrost supply. If you turn on AC, cold air comes out Defrost. Vent air comes out Defrost, etc.. Off works. Is this an expensive fix? What part is defective? Does the dash have to be taken out? Any thoughts are appreciated.

Sutton

And i thought i was the only one that had this problem. exactly like he said. The air temp. changes from heat to cool to a/c and so on but air only comes out the defrost vent.

ha ha... and then there was three... same here... but sometimes I can't even adjust the speed of the fans :\