Go to this site and click on "IHKA Components" for a description of the system plus there may be documented fixes as well (there's a lot of stuff). Anyway, go here:
http://bmwe32.student.utwente.nl/
If that doesn't work, consider registering at roadfly.org and post your question there. Johan, from the above site, is perhaps the expert on the heating and A/C of a 7-series.