Fun day with the 85 300CD AC center pod question...
 

So, I went down and had a local place charge up my AC system to test it. Turns out that MB did a full upgrade of the system to the newer stuff at some point in the past, sticker where there for it, but dates info long gone. Also the dryer, compressor etc are modern newer units. Got the gas in and what do ya know... AC! Ice cold AC.... But, it also showed another issue... a horrible squealing compressor belt... I have a good feeling that the PO in his total lack of any sort of upkeep whatsover, just let the system die once it started to squeal, or when the vac pod went out or? but whatever.

So for giggles I checked local parts store... 20 bucks for all 4 belts in stock... A real pain in the butt job, but will go easier next time. All the remaining belts where cracked and looked to be at a point of imminent failure, so I'm glad I replaced them.

Thing is, I can't get the center vents to blow... now, before you say it's the pods... I have tested them and they work fine. I can pull vac on them and make the center pods open and function manually with a mighty vac. What else could I do? does this sound like a flaky AC control unit or?

Check this thread and then check your defrost pod: (right foot)

http://www.peachparts.com/shopforum/general-information/295241-scans-airflow-w123-climate-control.html

If the defrost pod leaks in one or the other of its bladders, then the center pod can't get vacuum. I'm not exactly sure how the center pod check valve works, but I'd look at the defrost.

Great! I'll play with it tomorrow, thanks for the diagrams!