There Are doors that change position in the duct work that dictates where the air comes out when you change the selector it's possible that the selector circuit has came disconnected behind the panel or maybe the power circuit going to the selector has a short, broken line, or blown fuse. How ever it's a fair be that someone has had this problem. Try googling the exact car and exact problem. It could be a common issue and google will usually bring u a video of the repair procedure!