my battery does not stay charged,changed battery.terminals,had altenator checked on 1999 Cadillac Seville STS

I replaced the battery and it stayed charged for a couple of weeks

Asked by for the 1999 Cadillac Seville STS
1 answer
possibly alt is not charging under load, like lights on a/c on and so forth.have it tested under load even if its r/b or new