to brooklynbay. hope this finds it's way to you.This day was insightfull. The missing vac tube begins it's journey from the temp controls. You remove the clusters from the dash/radio and there is a multi ported vac cluster. Somewhere related to the temp control switch. You pull the switch out to be able to access the many vac lines.This isn't very precise but it's sort of correct, the many lines have different colors that identify their use. No one could equate a color to a unit, no one could sell me replacement tubing, a shop told me their method of repair was to put a larger size tube over the bad tube in a way that lenthens the tube and covers one good portion to another good piece. I guess I'll know the route from end to end when I tackle the fix,or replacement, I haven't decided yet.Hope this helps in a small way,I was glad someone got back to me so again,many thanks.