Unless I get a more definitive troubleshooting suggestion from someone I will proceed per LRG and dig in with a meter, 12V power supply...and try to trace the problem.

romansek said to check the 2-stage vacuum element. I already replaced it as well as the other faulty elements (per my first post above). Your offer for a diagram is very appreciated. As I mentioned my CD of the manual has a real bad scan of the wiring. The diagram I need is from the Climate Control manual (version III). The document is 83-603 "Function Test of Total System". I only need page 15 which is "Electric Wiring Diagram Automatic Climate Control Model 123.0, 123.1".

romansek: I will e-mail this pdf file from the CD so you can see exactly the diagram I need. You will notice that the wire lines are invisible because MB did such a bad job scanning this page. Hopefully for me you can do a high enough resolution scan from your paper manual so I can see all the traces. Thank you in advance.

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1972 450SL
1982 300D Turbo