My heat and airconditioning are working fine, except that as the driver's manual says, I should be getting air from my center vents when certain buttons are pushed. It also says that cooled or heated air should be coming out of the rear vent in the console between the seats. This vent is presently only producing fresh air at this time.

I looked at a diagram of the vacuum and vapor hose system for this car. Over the summer I had an intermittant problem with not getting much cool air through the center vents in the dash. When I heard a certain flap close - all of the sudden the air flow would increase and air started blowing from the center vents in the dash. It was like in my wife's Honda accord when you put the system on recirculate you get a lot more air flow than fresh air only. I noticed in the diagram for my 1982 300sd that there is a #41 vacuum element for fresh air/recirculating air. I am wondering if this might be the problem for both the rear seat console vent and the non-existent air flow through the center vents in the dash. There is also a switchover valve #18 in the diagram for the fresh air/recirculating air flap. Could this be an issue too and where are these two items located?

Has anyone ever replaced theirs??