[RonMar]

What is the actual voltage at the battery when running? If it is constantly feeding 30 amps, it sounds like the voltage regulator is fried. You might be surprised to find that the alternator is currently outputting a really high voltage(18-20+V). The battery boiling and absorbing the excess energy is probably the only thing keeping any other electronics in the vehicle from frying. I bet your lights are really bright too... This constant overcharge also outgasses a lot of hydrogen gas, which if provided a source of ignition can cause a battery explosion.

The AVR on a one wire is internal, and you may be able to get just that part, but is anything else wrong with the alt such as a diode in the rectifier? You might be able to overhaul it yourself cheaper than a replacement, but it can be an involved process splitting the case. I would say it is probably way easier to replace the whole assembly.

I would not put a switch on the alternator output circuit. First off you will need a big switch(30+ amp?). If the regulator is still partly working, disconnecting the load causes voltage spikes that can finish frying the regulator and you won't have any idea what it is outputting when you switch it back on. Also if it is putting out a higher voltage into the battery load now, when you disconnect it, the voltage will go up. When you turn it back on, you may send a high voltage spike into the system that will frag other electricals such as electrical engine instrunments.

I would suggest you do one of he following:

1. Replace the alternator and restore the system to normal.
2 you could disconnect the alternator completely, and add a small plug in trickle charger to keep the battery charged when it is parked. As long as you don't need lights for any significant ammount of time, and only need to start the engine, this will work. I have seen people do this for years on electric start mowers and small machinery.

Good Luck