Thanks, it's quite helpful, I just dont have the time to rebuild one car and figure out the other haha.
Anyway I got out there just now and looked, all the lines are hooked up properly - unfortunately. So that puts me back at the starting point. The red plug (looks rubbery) sitting under the front header, seems like its resting accross the kmember, is something I wonder about. I couldn't get a picture of it, my hands were so cold my phone thought I didn't have fingers.
I'll try to warm up a bit and head back out to try and get a picture.
Knowing the lines are all fine, what else could be affecting the vents functions?