Can bad alternator drain battery while car is off?

[martyf250]

still trying to figure out my electrical issue. Can a bad alternator drain my battery (fully charged) overnight while the car is off?

[eieio]

still trying to figure out my electrical issue. Can a bad alternator drain my battery (fully charged) overnight while the car is off?

yes, Marty..........
from my post in your other topic on this matter...........

and it seems to me that there have been alternator failures causing the battery to drain while parked

[martyf250]

thank you for the reply and help!

[eieio]

thank you for the reply and help!

.......you're welcome

[smj999smj]

The alternator can short-circuit internally, which would create a significant parasitic draw when the engine was not running. To do an overnight test, you could remove the alternator fusible link; it's often the one with the highest amperage and, depending on year/model, will usually be in the 75A-140A range. If easily accessible, you could also just disconnect the large wire to the back side of the alternator (at the "BAT" connection post). It'll be held on with a 10MM nut.

[martyf250]

was indeed the alternator. appreciate everyone's help who replied