Hi,

Long story short, a blunder was made in the dark late at night and the battery on my w639 was hooked up to the wrong poles.
This fried the sam unit which has now been replaced and the alternator stopped charging. I figured the diodes were fried so I got my hands on an unused and new alternator on the second hand market.
After installing it today the car still wont take any charging. I am reading the following error message:

2245-004 The signal from component G2/6 (alternator) is faulty. Communication fault between control module N3/20 (common rail(CDI)) and G2/6 (alternator)

With the car running I am getting 1.6V when connecting voltmeter to B+ on alternator and the - on the battery. If I remove the communication cable on the alternator this drops to 0.3V.

I am guessing it could be a faulty voltage regulator but since I have had the same problem ln two alternators I am led to believe the issue is elsewhere.
Any tips on how to solve this? I am having some issue figuring out where this communication cable ends up.