With the radiator fan, AC fan and the stereo amp, my alternator can't keep up. It is a GM 1-wire 10si (65 amp - I think).

Is it possible to put too big of an alternator on. I see 100 AMP, 140 AMP and 200 Amp available.

Does the internal regulator keep it from over charging if you are not using that much?

 

Current is drawn, not applied so technically the size of the alternator doesn't matter. BUT - the wiring must be sized sufficiently to handle all the load it will see, plus a margin for safety.

 

Makes sense, thanks.

 

Make sure to buy a quality piece. 65 amp alternator is way under powered as at idle it might put 45-50 on a great day. Take away what it takes to run the truck, lights, fans, etc and you are out of power quick. I just did one on a 48 Chevy where he had a one wire deal...as soon as a/c or rad fan went on it dropped below 12 volts immediately. Put a 140amp alt on it and it was unreal..not even a flicker. As stated before make sure wires and connections are great as well as a decent CA battery and you will be more than pleased with a bigger alt.