IGNORE POST BELOW: for some reason I thought I was in the e53 forum....OOPS.
To make up for my enormous goof...perhaps there's something in this e70 X5 Climate control PDF:
http://www.bmwmotorsports.org/pdf/e7...%20Systems.pdf
Nice complex question. 
I would suggest searching the internet for BMW tech PDF documents that center around the IHKA/climate control systems that begin with the e38...which was the first model of that generation where that newer technology was adopted by the next gen 3/5/X series (e46/e39/e52/e53).
Some of your answers may be buried in some of the info below. The IHKA (automatic climate control system) can get pretty complex...perhaps too complex in some ways. 