Climate control unit in the audi A8 changed

Hello,

In my A8 2.8 bj.95 because of one possible. defective the climate control unit changed. the difference to the old part was the end letter "c". I have the problem that the compressor for approx. 1 minute click klag makes, so try to turn on and then switch to econ. econ can only turn off again when the ignition was off!
error memory says 01270 - magnetic coupling for air conditioning (N25) 42-00 - speed deviation too large. I haven't had this problem before, can it be that the car with the other end number doesn't get along, or do I have to register the newer part somehow, if someone has an instruction how to do this? if I have to recode it then I need the login codes of the air conditioning system and these should be in the rep guide audi A8 from 94 air conditioning!
Does anyone have this guide with the appropriate codes?
doesn't necessarily want to drive to audio because of bad experiences!

Greetings
dieter