96 C4 AC/Heat Blower/Vent problem

My AC/Heat works great but it will not switch from blowing from the floor vents to blowing out the dash vents, it use to do it aftewr a few minutes or so but now it has stopped doing it and stay on the
floor vents no matter what switch location i put it on,should I assume since I am having problems with my Cruise that I have a vacum problem thats related to the venting system? I have the climate control option. Any help appreciated.
Dave
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snipped-for-privacy@aol.com wrote:

I had both symptoms in my '93. The vacuum check valves had gotten brittle and cracked. It took several times to the dealer to get them all, but now both dash controls, and cruise control are working well again.
Jim
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wrote:

Boy, that sucks ;-))
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wrote:

Ditto on my 96 Rob
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Same w/ my '93. The culprit was located on the passenger-side under the "Corvette" engine shield over the manifold. Just follow the vacuum lines to identify it. Problem with mine was a crack in the neck of a barb that entered the check proper. I was able to use some silicone to repair the connection and now everything works fine. Good luck to anyone with the same problem.
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Mine is stuck such that it only blows on the widshield, I have the GM service manual but it refers you to 95 service manual for details of the plenum valve that controls this re-direction function. Looks like a tough problem to find and fix. Let me now if find out how --- i'll do likewise
'96vette

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Dave,
My '96 started doing exactly the same thing. The dealer thought it was a computer problem and yours may very well be a vacuum problem but the fix for mine was simply to refill the Freon and fix a slow leak. It seems that the AC computer doesn't want to blow warm air in your face so it waits until the evaporator coil gets cold enough before turning on the dash vents which normally takes less than a minute. As you lose Freon this takes longer and longer until the AC can't get the coil cool enough to convince the computer to enable the dash vents. It's still cooling and the floor vents feel cool but apparently not enough. The C5's don't do this so I assume Chevrolet realized it was a problem.
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