AC air vents problem 89 OLDS Delta 88 Brougham

I can't control my output air vents on the AC. As of 3 days ago Air comes out the defrost vents only. The direction indicator lights work but there is no change of air flow to the floor or dash vents. Before I stick my head in there it would help to know if this car has a climate control computer or is vacumn used to operate the changing of the air flow.
Come on down!