Since I pulled the Argosy into the shop a few weeks ago, in my spare time I've tinkering with various parts trying to get them ready for installation. Several years ago I dismantled the heater/evaporator box for the dash air system. When I took it apart I found that the hinges for the two flapper gates (fresh air in and air to cockpit) were rusted solid. The fresh air in was frozen open and the air to the cab was partially open.
I've since freed the flappers up using electrolysis although the fresh air flapper is still stiff so I'll likely replace the hinge.
The picture below was taken from the outside of the box looking through the fresh air inlet opening. The expanded metal in the back of the box is the opening into the cockpit by the passengers feet.
When the unit is set for fresh air both flappers are open and their is a direct path from outside straight to the passengers feet.
What I'm wondering is, is how important is the fresh air vent? If I remember correctly we used it from time to time on the 310 but for the most part the dash AC was preferred.
Assuming I leave the vent in place would it be a good good idea to baffle the vent so rain can't be blown straight into it?