Alternator on ignition off

[Cannman07]

I just replaced the alternator as it wasn't charging and I had the battery light staying on. Now when the ignition is off there is a tiny high pitched whine coming from the secondhand alternator I've installed. The battery light was on with the old alternator but is now off but I can't work out what is making the whining noise from the alternator. If I disconnect the battery it stops and it starts again as soon as the battery is connected.

 

[mirrabucca]

I just replaced the alternator as it wasn't charging and I had the battery light staying on. Now when the ignition is off there is a tiny high pitched whine coming from the secondhand alternator I've installed. The battery light was on with the old alternator but is now off but I can't work out what is making the whining noise from the alternator. If I disconnect the battery it stops and it starts again as soon as the battery is connected.

No responses?
It sounds like the replacement alternator is faulty.
With the dash in diagnostic mode, does the alternator charge normally?
If you leave it overnight does the battery discharge?

With the battery disconnected, disconnect the alternator at both connections, then test it. Then touch the main alternator cable onto the connector at the alternator - see if the noise starts. Then do the same with the regulator connector (the plug-in one).
If one of the diodes in the alternaot is blown (short circuit) battery current will flow through the alternator windings. That may be causing the noise.
If that's the case, then the charge voltage will be low.