Alternator is not charging (I used the search before asking)

[Turambar]

I pulled the 250 from my '79 and dropped in a rebuilt 350. Everything seems to be running great... except the alternator. I am at a complete loss... I have searched the forum for at least an hour before posting, so I am hoping to get some help.

A few pics...



The two wires in my hand were in the original alternator plug. The truck ran (barely) when I got it back. I didn't check the voltage gauge the few times I started it to see if the alternator is working. The plug was completely messed up, so I cut them and spliced new wire on to a new plug going into the alternator.

With the truck off or on, the red wire is not getting any power. Neither is the black (I think that is the color) wire.



I couldn't show clearly in a pic where the black wire goes in, but the one on the top left is where the red wire can be traced back.



This is the second of two alternators I had tested at O'Reilly's. Both tested working. In this pic, you can see one of the things I have tried. I went from the 2 plug on the alternator to the battery screw on the back. The white wire is connected to the "black" wire from the earlier pic, but like I said before, it is not getting any voltage with the truck on or off. The voltage from that screw reads the same as the battery (about 12.3 v). My battery is well grounded. The truck starts up just fine, but the alternator is not working. So I am on the 2nd alternator, and I still am not charging. My understanding is that I should be at 13-14 v if the alternator is working. I did remove the positive battery cable while the engine was running, and it did immediately die.

So wiring gurus, please help me. I am at a complete loss.