charging issue has me stumped

[drfong]

Hi all. I have a charging system question. It's an old TRX200. Very early 4 wheeler. Has about the most basic charging system. It's a two wire stator, a four wire reg/rec and a battery. I first thought it was the stator but it is not grounded and the resistance is right where the manual says it should be. The wires from the stator are in great shape all the way to the regulator. The conection is good at the plug. The other 2 wires to the reg are the +battery and the ground. Both are good. There is full battery voltage at the plug and the ground has no resitance. That would leave the regulator so I ordered 1 and no joy so I got another one and same thing. All three do the same thing. (they were both off running working bikes). I also made sure the regs were mounted with good ground.
I then thought maybe the stator was still bad eventhough it checked ok, so I unpluged it and ran the motor and checked for ac voltage. There was no check for this in the manual so from memory I believe you check AC across the two stator wires. When you rev it up you get about 70 volts ac. So that seem right to me. I even changed the battery to make sure it was not something there. No Luck. It always does the same thing. Here's the run down.
Key off about 12.2 volts
Key on 11.5 volts
Running at idle about 11.5
Reved up maxes out at 11.9 volts
If you run it for awhile, eventually the battery goes dead.

Any ideas?

[Here 2 help]

Although you had 70 volts AC, I presume the check was made on an open circuit. Try checking the AC output with everything connected and the engine "revved up". My guess is your stator has an internal short and the AC output will be low. You need something over about 18 volts AC to get enough DC to charge the battery.

The stator probably shorts out under load. You might have (and it's rare) a bad rotor. Sometimes the magnet gets weak and there is no test for that with simple shop tools.

[drfong]

Thanks for the reply. What I figured out today. The lights are always on as the handle bar switch didn't work. I unpluged the light and the charging system works. Puts out almost 14 volts. Strange thing is voltage drops a bit when started then starts to climb. Only puts out about 12.5. When you rev it up it starts to put out more and will put out close to 14. Then when you let it idle it still puts out about 12.8 to 13.1. It'slike it has to get to a certian voltage before it really starts to work. Then you can turn the light on and it will still stay above 12.5. But if you turn it off and start it with the lights on it never will charge. Could just be because it's old or just a weak system to begine with and they really wernt designed to run the lights all the time. But I fixed the light switch so I can shut off the lights and it will keep the battery charged just fine.
Thanks

[Here 2 help]

Yeah, the older machines were not intended to run with the lights on 24/7