Center vents do not open, climate control unit or no?
 

My center vents do not open, otherwise the climate control seems to work fine. My indie seems to think its the climate control unit itself, but they seem to run $400 for rebuilt ones. Before spending this money is there anything else to check?

Check this source out. I have found them fast reliable and reasonable. You can also call and talk to them.
http://www.thepartssite.com/pages/mercedes.html

center vents
 

try running a self diagnostic in your system here is a link from bobterry99http://www.peachparts.com/shopforum/showthread.php?t=86546

Doc,

If you have any leaks or a bad vaccum pump it will not work either. I found leaks between the engine and firewall and going down to the transmission where the exhaust burns the lines. Also in the trunk where battery acid melted the line going from the pump to the accumulator. Spent lots of time and disassembly but no parts or high priced labor.

I know he's looking for a replacement control module, but I'd lay 3-1 that the module is okay and the trouble is vacuum related...

my indie is very positive its the pushbutton unit, but I really doubt he went thru all the vacuum lines. I just got a new transmission as well so am wondering if something could have been unplugged.

I'll have him take a closer look at the lines.