1990 Plymouth Voyager Alternator not Charging

Electrical problem
1990 Plymouth Voyager 6 cyl Front Wheel Drive Automatic

I am working on a Voyager for my neighbor that has had a Alternator charging problem, its not charging. We removed the alternator and took it to a local Auto Zone for testing and it checks out good. So we reinstalled it and started checking the wiring. So far if I put a volt meter directly off the Alternator at the positive post and the ground post I get no voltage with the engine running I disconnected the positive power wire from the alternator to the battery so I dont get ant false reading. Second I checked the green wire coming from the control module for a negative supply at the alternator and that turns to be good wile the engine is running. Than I checked the supply voltage from the blue wire to the alternator and I get a good 12v there while the engine is running. Everything checks out good to the best of my knowledge but still no charging voltage off the alternator. My instinct tells me it is still a bad alternator but tests tell me otherwise. What else could it BE?