Hey guys,,got a weird problem,,ive got a 89 ,mass air,set up,5.0,,anytime i rev it past 2600+ my altenator light comes on,and it full fields,,optima in trunk,2 gage cable,grownd in trunk,grownd from eng to body,even put a grownd from alt to body,,just in case,both positive feeds at big plug (3 wire) has 14.45 at idle,,small white/black stripe has 7.53v,,,so does the yellow/white strip on second plug,,but other 2 wires on plug showing -7.50v,, very strange? something is causing it to overcharge,,if i put my electric cooling fan on,then the voltage jumps to almost 15v,,everything is new,so i dont get it,,any ideas??? let me know,,thanks,,,,DRIVER.,,note problem was there before i put grownd from alt bracket to body.

 

Thats odd, Im not sure.
When I did my Battery relocate kit I ran a ground from my battery right to my transmission, then one from the battery to the body, and another one from the engine to the body.
I don't have any problems.

How new is your alternator?