1984 Cutlass Supereme - AC airflow issue
 

Hi all,

When running my AC on MAX, I noticed I am losing quite a bit of airflow at the floor vents. These are supposed to close and all air should be coming out of the upper vents.

Any idea what is causing this? Airflow goes up to the defrost vents fine. I know there is a vac tank under the hood whose purpose is to somehow control vacuum for this... If it were bad I wouldn't think I would get airflow to the defrost vents....

Thanks!