I have a 1966 Olds 98 with A/C and I cannot get my defrost or floor vents to work. Help!!!

 

Check those vacum hoses! These systems work off engine vacum to open and close all the dampers to direct air where its needed. Most importantly, there should be a check valve between the intake manifold and the vacum storage tank. from there it should 't' off and feed your control cluster under the dash. Have you noticed a sucking sound when ever your try to use defrost/heat settings? Could be the leak is inside the cabin. split hose, bad diaphram in the damper motors, bad check valve(preventing the tank from maintaining any vacum in it at part cruse/W.O.T.) can all cause problems. Here's a quik schematic. maybe it will be of some use.