[W126 Coupe] Climate control quit working

[Dan Stratton]

I mentioned a problem with my climate control the other day and found  
out it was a fuse (Don't ever depend on 55+ year old eyes to see a  
blown fuse). But the cause of the fuse blowing has me stumped. I would  
like to disable everything on that circuit to find the problem, but  
where to start? Where is the aux water pump located (and does it plug  
in?) What is the likely culprit? Yep, I know it could be anything on  
that circuit...

Dan