Alright im hooking up an external regulator (One of them blue boxes) to a second alternator that is separate from the vehicles electrical. . There is 3 pins in the plug on the alt but right now there is just one wire going to it to turn it on. ..  The problem I am having is I dont know where to hook the field wire from the regulator to . I have tried the all the pins in the plug of the alt but nothing is making the regulator work .  . 

 

Vehicle is an 08 escalade and the alt is a dc 370

I need to find where the field wire is on an internally regulated alt . 

Why are you setting this up separately ?? Different charging voltage ???

Thats what the guy wants .  Said his computer in the car alot of the time is makes it just charge at 12 something

If that alternator is set at 13.6 (normal 12 volt charging), there is no need for a voltage regulator. 

If that's a DC alternator, ask the manufacturer for a wiring diagram.