The earlier W126 had the same system as the "second-gen" W123. I'm not sure at what point they transitioned to a different climate control setup on the W126.
Assuming you have the same system as mine, then you'll have all the same components but just located in different areas. For example, the blower control and temp control units are both behind the glove box on my car but are down next to the blower on your car, as you mentioned.
However, even if you do have the later system that page does have pin layouts and diagnostic steps if you scroll up a bit.
To help identify which you have, if you have a panel that looks like this, with the thin white AUTO button, your system is the same as mine:
