[RegB]

I have a 1999 BMW 323i E46 and the alternator is not charging and I am getting the battery light and check engine light on dash. I am not a mechanic but have gone through the following steps and still have not found the problem with alternator.
1) Replaced battery with new battery
2) Removed Alternator and had it tested 3 times and test all came back good. I believe on the test it showed 14.4V
3) Check voltage at battery, jump box under the hood and red wire going to back of battery with car not running and all were same (12+V)
4) Installed new drive belt, new tensioner pulley and new idler pulley
5) Still not charging. With car running I checked voltage at back of alternator, jump box and battery and they were showing below 12V. I assume it was below 12 because car was running on battery only.
6)Checked grounding on car - I assume it is the main grounding wire is the one that I found on the passenger side front near a front sway bar? I removed the ground wire and cleaned it and also had it checked at auto parts and they said it was good.
7) Checked all fuses in the fuse box in the glove box.

At this point I really do not know what else to check. If any one has any ideas please let me know. Thank you and I appreciate your support.