Pontiac Repair: battery not charging, pontiac montana sv6, delco alternator

Question
QUESTION: ok i got a new alternator because the battery light came on. now that i got the
new alternator still the battery light comes on and the battery is only 3 months
old and i already took it to get it tested but they told me the battery is good. any suggestion

ANSWER: Hi Edgar:

what model and year cars is this?


---------- FOLLOW-UP ----------

QUESTION: its a 05 pontiac montana sv6 3.5.

Answer
Hey Edgar:

Did the light go off for a while and now it cam back on? did you put an ac Delco alternator in this van or an aftermarket one? The laternator on that van is controled by the engine control module. The laternator controls the field in the laternator which is the amount the alternator charges. If the lamp wnet out for a while and came back on again and it is indeed an aftermarket alternator I would suspect that the alternator went bad again. I AM NOT A FAN of any aftermarket electrical parts on any kind of car or van domestic or import. If the lamp has been on all along I would suspect either a bad connection,wiring issue or a bad engine control module. Most of the time it's the alternator. Good luck :)