Originally Posted by Frank4
Thanks for all the info, I have not had the time to go out and work on it. Sounds like a vac problem. Dose anyone happen to know where behind the dash the lines and vac are located?
The "Vac" is developed by the engine intake manifold. Usually it - feeds a small volume chamber for the vent system. You need to spend a little time moving stuff around under there. You'll see hoses leading to a distribution box, thats where the valves will be with small vacuum hoses on each valve. Another to change position of controls while you watch/listen.
By the way, vehicle codes mandate the system must default to defrost in case of failure. Allows driver to see in bad weather. Problem could be large leak in vac supply or even severely crimped hose, happens when rubber ages, esp in engine compartment.