I've been working on a 1997 E 420 that has different temperatures from the left and right vents. The outside temp. gauge reads properly and the duo-valve,refrigerent charge and vaccum systems all seem to be working normally. No matter where the temp. is set the left side blows warm, not hot air. I seem to remember reading a similar post a while back but I couldn't find it with a search. Has anyone run into a similar problem.
Thanks for your help.

I've encountered the same problem with a 140 chassis car and it turned out to be the vacuum switchover valve. Steve Brotherman gave me the post for this problem if I remember correctly.

Something to do with a vacuum leak. Check out these two posts on the subject.

http://www.peachparts.com/shopforum/showthread.php?threadid=17822

http://www.peachparts.com/shopforum/showthread.php?threadid=17129