2005 XC90 T6 Alternator light on and draining battery

[roncop]

Last year my check charging system came on while driving. I pulled into a garage and discovered I was only charging at 13 amps.
I replaced the alternator and the dash warning light as well as the check system still indicated "charging problems"
I have changed the unit 3 times with Bosch equipment and I still have the lights and warning on. Now if I leave my car for 4 days without running, the battery goes deader than a doornail! I have installed a new battery and same issue. Did a scan and 2 codes appeared, DD21 and DD30. Both have as symptoms "will drain battery"
There are only 2 alternators available for my vehicle according to the dealer, a 140 amp and a 160 amp.
I have the 160. The regulator box is apparantly very unique in 2005/06 on the T6.
I'm not sure what to do because its about 3 hours labor every time to change the alternator.
Has anyone had this problem? Are there other know causes besides the alternator?
Thanks,
Desperate Roncop