TJTJ are you able to explain how the amperage is controlled / regulated? Just curious.
I know there is a voltage regulator so when it is "on" it will give a steady voltage. I also know the amps will vary via RPM. I just did not know if we had a solid state solenoid in line to turn on and off the Alternator to prevent from overcharging.
Correct, just add that, as the voltage is trying to be kept constant, the voltage regulator is increasing the amps to maintain that voltage when the demand goes up. The output is controlled by the rectifiers in that part...and if the rectifiers are recti-fried, well, the current is not regulated anymore, or, at least, not as well as it needs to be, etc.
Depending upon which diodes get fried/damaged, etc...you can sometimes even maintain voltage, but amps are uncontrolled, etc....which can mean too low an amp or too high an amp supply, etc.
I find that this is the main limitation on rebuilt alternators, at least for me...as the PepBoys, etc, techs have told me a used alternator was fine, but, the rectifier diodes were shot, and it wasn't fine at all...it was a paper weight, etc.
So the load, if low enough, say on an Autozombie test bench, might be within the remaining voltage/amp capacity...so they call it a good alternator. If the loads are increased, as its typically a stepped test when done the "real way", you can better see if a diode is burned out, etc.
I found a local alternator/generator shop, and THEY can do real tests that are more definitive, and, I skip the big box moppets and go there with a questionable alternator find instead.