What's the voltage at the battery posts after running a while? If it's over 7.5, the voltage regulator points are stuck (the coil behind the Field wire) or there'a a grounded spot sonewhere in the field wire between the generator and regulator. It's also possible the battery just has a low state of charge and the generator is trying to recharge it. That would require driving for several hours without running the starter. Charge the battery overnight or longer and see if the problem goes away.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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