My alternator went out on me and i replaced it but still not working on 2003 Cadillac DeVille

dash still says battery not charging, service charging system what could it be? Sometimes it kicks back on but then go back to battery not charging. that's also how it started before just completely out

Asked by for the 2003 Cadillac DeVille
Many newer vehicles now use the PCM to control the alternator. I recommend have an electrical system test performed. Without being able to see what the PCM is doing you will just continue to throw parts at it.