organcory

It looks like it is the battery and the alternator. The alternator was only putting out 10.

organcory

Alright, now I am confused. I replaced the battery, alternator and alternator wiring harness because it was slap worn out, I still get 12.9 V when the car is sitting and when I turn the car on I get 12.5 volts. What am I doing wrong or what else can i check?

Colorado_Mustang

Voltage regulator.

organcory

Where is the voltage regulator - by the headlights? I have a square box on the front near the radiator with a plug in the side.

Colorado_Mustang

It's by the battery. It has a plug on the side with 4 terminals. Your alternator harness will plug into it. It's basically just a square and will be 2-4 inches in depth.