My alternator light started coming onsometimes this weekend, when the truck is at low rpms, if I get the rpms over 1500 rpm the light fades and goes out. This leads me to believe that the problem is with the alternator and not the regulator? Is it possible that it is a loose wire or is my alternator on it's way out? It's from an auto wreckers and was in the truck already when I bought it.

 

diodes probably bad in the alternator, replace alt.