Check out this site
http://www.powermastermotorsports.co...ternators.html There is a lot of good info here and these guys may be willing the help. You need to ID your alt and weather or not it is a one wire type and who made it. Then you can work on finding out what your alt needs from your car(wiring) to operate properly. Then you will need to properly determine what each wire in your cars harness is providing to the alt. I does sound like you have a one wire alt and you are connecting it incorrectly. The fact that you performed an expensive test of changing the alt and battery and the problem is the same eliminates these items.