Check the volts at the charge wire at the alternator see what that looks like ... An alternator turns into a big magnet if it working so a screw driver will stick to a good one at the back ware the rear bearing is ...The reg could be half bad and its only charging at high RPM's or stops charge at high rpms and just charges at low rpm's ..

Whats the volts at the battery and at the alt when its running ??? 12 volts ? 19 volts? 10 volts ? ??

You need more then 12 volts to charge a battery and 15 volts cooks the water out of a battery and kills it ..

Bad brushes can make a ALT come and go .. There only hitting the rotor every now and then do to being to short ...

Hope you get it fixed

David

Hazardous Toys inc ...