Hey guys and gals,

Many of you have been writing things about the problem of vents closing and no air blowing out under acceleration. I've had the same problem for a couple months now. The FAQ gives some information about the 2 way valve that is impossible to reach under the dash. I was contemplating going in there and trying to replace this, but I found another source of my problem that I wanted to share. BTW this was not my finding, it's been mentioned on this board numerous times by several great bricksters.

Anyway, check the black/white vacuum check valve near the firewall under the hood first. This part is very cheap and easy to check. In order to check the valve, just remove it and blow into both sides gently. If air goes through only one way then you are fine and this isn't it. If air goes through in both directions then you have a bad check valve.

In my case I was loosing vacuum pressure because of the bad check valve. Then when I was under acceleration I was loosing even more vacuum, causing no air to come out of my front vents. It was being diverted to the defroster. Now that the valve is in place, my vents have enough vacuum to work fine, even going up hill under acceleration.

Anyway, I just wanted to share. Good luck.