Regarding the air vents in the back of the 1968 Corvettes.

There is nothing involved other than a rubber flapper which opens and lets air flow out when there is any increase in air pressure inside the enclosed cockpit. When I have the windows up the "Astro Ventilation" ducts can be opened to allow cool air to flow into the cockpit from the bottom area of the dash.

The system is great when you have the top on and a window open as it reduces the buffeting that normally occurs.
A lot of the older C3's have rubber flappers that have hardened up and no longer are effective. Dr. Rebuild can get you going real soon and it is very easy to fix.

I can not say that C3's with AC don't have some other control mechanism using vacuum back there but the non-AC Vettes in '68 have a great system that is incredibly simple.

Christopher T. McCloskey

Hey, this could be why there is hot air coming into the cockpit, right? I tried to find something about the Astroventilation stuff in my owner's manual, but there was very little about it. How do I turn it on and off?

My windows say Astroventilation on it, and I saw the flaps in the back when I was replacing the gas tank!

Imran - 74 Convt

I've considered the valve on the heater hose but Western Pa is one of the few places where ou may need heat in the morning and A/C in the afternoon...

So...are you all saying that the auto shut-off valve is not very efficient in stopping coolant from circulating when the A/C MAX is selected?

James et al:
The part numbers for autopartsgiant.com (20500 & 20501) I have found no way to find them in their online catalog. Can you give a hint as to how to find them so I can get them on order?

Thanks,