why is my car still running off the battery? 2000 grand am v6

was the battery FULLY CHARGED when you changed the alternator ? If not , a less than fully charged battery will fry a new alternator the first time you start it after replacing the alt . reason ? too much current draw to operate all systems plus put 40 or 50 amps back into the battery . The antilock brakes alone take over 50 amps . onboard computer : 35 amps cooling fans 40amps ,AC, 20 amps . get the idea ? your new alt is probably fried . Charge the batt fully before replacing the next one (alt)

Funny this should come up, I am literally sitting on my front porch right now after installing a new alternator ('01 BMW 540i 6 speed) waiting for the charger to finish. I was searching google for anxious to see how close the charging is. Got bored after google was inconclusive... Using a black and decker multi cycle charger that went from like 5.7 amps to now 1.9... jobs been done for over an hour. I am however less inclined now to "see if it will work" or if it's "close enough". Not impatient to replace another alternator though. Saved myself over $800 vs. the local indy DIY. Now an exercise in further patience after waiting on parts and a nice day.

yes brand new battery brand new all three when i turned it on!!!

oh also the starter doesnt disengage properly

I am not a newer car person but I'd say the starter may either be loose or maybe it too needs replaced . did this car ever get driven through deep water or sit for a while where it was wet ? (for a while means a month or so ) PBN

i have the same car what i understand its the pmc computer and the starter getting stuck could be the same or again the pmc