Fresh Air Vent

[EV2AAR]

Recently purchased a 73 Swinger it was a 318 air cond car, the AC is lond gone and the heater core is disconnected. Am still driving the car and I would like to stop the fresh air from coming into the cabin. How do I do this manually
since I'm unsure if the cables do anything.
Thanks in advance

 

[whitey]

I'm not sure if I'm right but i'll give it a try since my 73 has been redone and I got rid of the AC and put in a heater/fresh air box and air box on the D/S.
There are alot of vaccum lines, try to find one of the vacuum diphrams and see if you can move the linkage to close the flaps.