If the alternator indicator is bouncing around or showing discharge at idle the alternator might just have a pully that us too large. I went from the rebuilders favorite about 2.75 inch dia to the stock about 2.5 and the guage is calm now.
this kind of sounds like maybe my problem , when I check the output there is nothing when I check the out put at the alternator it kinda bounces with my test meter , where did you get a smaller pulley?
