Hello Peter,
my name is Alexander Maier and i am new in this forum. I live in Stuttgart Germany and own a 1990 964 C4 without ac since 4 month. Reading one of your requests in the forum regarding all fans does not work, i came to the conclusion that i have the same issue in my car. I tried to search german forums as well but seems to be you are the only person who had this problem - except me. Hopefully you could tell me the reason for this issue and how you fixed it (was it the DME or was the CCU faulty or anything else ?) Sorry for my bad english. I would be happy to get some information from you.
Regards
Alexander