The OBD I have is a Porsche specific one so it access all areas of the car. And yes I can read at least 20 parameters within the AC system. It is very comprehensive and all parameters related to AC seemed to be within spec. But, will review the parameter to make sure they are in spec and not missing anything.
Also, if I scan the car without the AC module connected it accuses the module is missing and it could only know that through the canbus as you can see in the diagram attached there are no ID lines. This supports your theory that the unit is working, communicating with the ECU and the problem is somewhere else.