Alternator problems? not too sure

a couple days ago i got my alternator replaced, and bought a brand new battery. the alternator was from the junkyard. well, now my battery is getting drained within a matter of hours. i went to advance auto and NTB to get it tested, and they said it was working fine. before my previous alternator went out, the battery never got drained or anything, and i’m having to disconnect the battery every time i’m done driving it. they said there were no crossed wires and that the wires were hooked up right. PLEASE HELP!!!

When they said “it was working fine” I’ll assume you are referring to the alternator. They probably checked the output, and yes, maybe it was putting out the correct amount of current. But what if your alternator was causing a large parasitic drain on your battery. I would suspect that. You can remove a battery cable (any one) and lightly touch it back to the battery post. See a small spark? Now disconnect the electrical wires from the alternator, and try the small spark test again. Did the spark get a lot smaller? If so, you have a bad alternator.

Since the alternator checks out ok (and I assume it was removed from the car to make the check) then the trouble would have to be in the wiring to the alternator. Make sure the warning light for the charging system turns on when you turn the key from Off to ON. If that is ok then check to see if all the wires on the back of the alternator have near battery voltage on them while the engine is running.

It could be a new parasitic drain on the battery.