[frankc]

Javadog,

Yes, that is strange indeed. I can see from the photos of your white and brown cars that both have what the PET diagrams indicate as being the non-A/C style control boxes. So did the A/C blower supply cool air to only the center vent in the brown car (before you removed it)? Or did it also feed into the control boxes somehow? From what I have seen in the 911, Porsche always kept the A/C and non-A/C air separated via independent ducts, so the latter would be odd.

I just can't imagine the center vent alone being able to supply enough air to cool the cabin, but then again the side dash vents are so small (on the pre-84 cars) that they probably don't contribute a whole lot of additional volume anyway.

Yes, certainly a mystery.