Dave,
The "charge indicator light" can be sort of misleading. It indicates the state of the battery charge. But it does not indicate if the battery is “charging.” The manual states, but I don’t remember the exact voltage, but the light come on when the battery voltage drops below a certain point. Like 12.8 volts (or something like that.) Then the light turns off when the battery has reached the correct charge level.
Your statement would indicate that the PTO is using more current than the system can provide. Once it turned off, the system brings the battery back up to the voltage required to turn off the light.
I’d say your problem is not the charge indicator, but either the PTO is wearing out and using more voltage than it should, or the voltage regulator/generator is misbehaving.
I’m sure someone will step in and give you a more detailed explanation and a way to track down the problem.
Good luck,
Joe