bruneau

My 77 ninety eight with 403 and tempmatic a/c had air only coming from floor vents. When I went under the hood I found the vent/actuator lines were taped together against firewall. Only gray line directly to main vacuum manifold source. Nothing to or from vacuum ball. When I a attached new line from main source to ball I then was confused as now I had 4 colored vacuum lines (purple,pink,green and gray) left. If I attach purple line to out bound from ball air vents from all upper dash vent as it should. If I remove and place gray line at out bound it shifts back to floor. I did not try the rest as I was under the impression that there should only be another single black line to under dash and colored lines from under dash to control unitl.
is there another multi line port that should be under hood. At this time with purple line attached under hood to vacuum ball. Dash control has been overridden and any selection from dash level.remains with only upper a.c. vent air flow.
Any suggestions on this?

Olds64

The air doors in your Oldsmobile are vacuum actuated. If the vacuum isn't present the air doors default to defrost. Manifold vacuum needs to be routed to the vacuum reservoir and the colored vacuum lines need to be routed to the back of the AC control head. There should also be a vacuum line from the vacuum reservoir to the AC control head.

bruneau

Thanks for your asistance. I am not familiar with Gm systems, all the diagrams i found are exactly as you state. But there is no main line from inside car through firewall to vacuum ball. There is no line from ball to vacuum source. I have had car 3 years and the vents would change from heat to defrost to dash a.c. With no issues. Sometime it was slow to change from floor to dash. Then about a month ago started car and a.c. Was coming through flo r vents NO defrost at all, if you choose defrost Amir came from floor only. Under dash there are currently 5 or so colored lines from control head to various actuators. Any clues as to why there are also 5 or so matching lines outside firewall.and not one main line. If I push to lines back through firewal, where will the go? All the actuators already have lines attached. Right now with purple line attached i can change dash vents to defrost but no for at all also with purple line attached there's no heat only ac. Not so if gray line is attached you have heat and a.c. But only floor