I bought a service manual heating air con book for the 123. The thing is dated 1988.
It covers all 3 systems in really good detail. Now I see why every scan of the wiring diagrams suck! Those are the smallest numbers I've ever seen. I swear it's a friggen eye test. Now here is the real pisser. This 80dollar book doesn't mention the Klima relay at all!

So there is no way to see how the Klima interfaces with the rest of the system. What a joke!