I just pulled my alternator, the bearing started to go. Got a new one, installed it, but now I'm thinking to keep the old one and play with it.

You see people applying voltage to their alternators on YouTube and they run just fine. I can't get it to work though. I hook up my hot lead to the terminal and I attach the ground to the housing and nothing happens. What am I missing here? I've tried 12 and 24 volts from car batteries. Btw, it should work without the coil inside energized. This is according to the videos anyway.

 

Our alternators are actually three phase AC generators that have rectifiers that convert the AC to DC to charge the batteries. You would really need to supply the same AC to the three stator windings and I am not sure what would be needed on the rotor to make it work. There is more to it than meets the eye.
Back in the day of real generators on care you could make them run on a battery but not any more.

 

An alternator will not work as a motor. What you probably where looking at is that they were using them as a generator of even a welder.

 

This makes a lot of sense. I did some more digging on the subject and this seems to go along those lines. More research needed. Thanks.

 

This is for RTorrez1.

 

An alternator can be run as a motor - as mentioned, it's "natively" a three-phase AC generator with a rectifier assembly. You'd need to strip out the rectifier and apply 3-ph AC, as noted.

However, I have had good results connecting a generator (native DC) or alternator (AC rectified to DC) to a small engine to make a light-duty generator, in a pinch. Removing the rectifiers from an alternator and going with full battery voltage to the field coils will give you (I think) about 90VAC and a heavy available current - which is the idea behind the "weldernator," usually (a rheostat can be put in the feedline for the field coils to allow manual regulation of voltage/current output.)

I haven't worked with something like that in years, tho, so my memory is a bit foggy (I would normally do this with Motorola or Delco SI-series alternators, since they were plentiful and cheap. You could probably do it with a Ford or a Chrysler unit as well - I've just never bothered.)