A/C Vacuum Check Valve Problem?

Chasing down a blend door problem on a 2000 Taurus wagon. I only get air through the defrost ducts.
Following the pin-point tests for the mechanical side of this system, I
get to the A/C vacuum check valve, and it **does not** hold the specified 15 hg for one minute. Pin point test says to replace the valve.
However, while at a junk yard the other day I pulled about five of these valves from other Tauri and saw the same result. None held 15 hg for one minute.
I'm not convinced this part is the problem, and that buying a new one would be a waste of $11. The guy at the parts counter says he's never sold one of these to anyone before.
Any ideas?
Thanks
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snipped-for-privacy@optonline.net wrote:

esp since they cost 1.98 to make, incl overhead and burden.. and if they hold that vac for 15 seconds, that's not bad.
Unlit propane torch, engine running... do I have to spell it out?
<grin>
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Yeh, I'm a Krusty old Geezer, staving off dementia here..DEAL with it!

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snipped-for-privacy@optonline.net wrote:

Wait a minute... I was ASSUMING you see no movement of the blend door actuator/lever. If it DOES move, stop-stop, then it aint the vacuum.
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Yeh, I'm a Krusty old Geezer, staving off dementia here..DEAL with it!

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Well, if I'm only getting air out of the defrost ducts, is it safe to assume the doors are not moving? That the actuators are not getting the proper amount of vacuum? Hence the pin-point test on the check valve, and my query?
The propane trick won't work here. I'm not chasing an intake vacuum leak. I think I'm chasing a possible leak on the vacuum resevior that feeds the blend door actuators, but I defer to your seasoned guidance.
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snipped-for-privacy@optonline.net wrote:

1. It's safe to assume the door isnt moving... it isnt safe to assume the actuator isnt moving. Anecdotal evidence of the door breaking loose from the shaft.
2. It's a vacuum leak.. but that means air is being sucked in, not 'vacuum leaked out' And that air is sucked into... yep... the intake manifold.
also, of course, listen closely for 'hiss'
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