Charging problems

The alternator that's on it now is from my old 5th Ave at idle and fast idle it charges fine but once I up the rpms it goes above green into the red on my test meter. The factory gauge stays in the middle. I've tried two VR I had laying around plus a brand new one and they all do the same. I'll make sure there's a good ground tomorrow.

The wiring is pretty butchered I'm looking right now for aftermarket wiring harness
Found one on amazon 12 circuit made by A Team Performance never heard of them but it's $140.


The old alternator would only charge 12v.