I see that no one replied to you, Jim. I'm not familiar enough with the topic, and didn't read through them all, but you may find a lead somewhere in prior threads by searching this Forum, entering "air dryer valve". Use the Search button to the right of the Home and Help ones, above left; it's much more useful than the Search field that's above right. If you come across what appears to be a helpful thread, try replying to it; it may be a resurrectable thread.
If you haven't already, you might check the list of publications in Coach Assist also. And try asking in the forum at FMCA where you'd have to already be a member in order to be one here.
I'm sorry I couldn't answer your inquiry directly, but hopefully this reply provides some benefit. I hate to see initial posts go totally unanswered.
-Joel
