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Posted by David Sherman on Tuesday, March 24, 2009 at 02:27:44 :
In Reply to: overcharging update.... no success posted by T-roy on Monday, March 23, 2009 at 23:56:33 :
That voltage is definitely way too high. I wouldn't want it going much above 7.2 at high RPM. Assuming it's a DC generator and all the connections are good, the regulator has to be bad.
If it's an electromechanical one, take off the cover and push the arm on the voltage coil (the one with the finest wire) down by hand while it's running. This should open up the points and stop the charging. One in a while, I've had those points weld themselves together for reasons that aren't obvious and don't seem to repeat -- perhaps I accidentally shorted something with a tool. Once the point are unstuck, it works fine.
If their not stuck, then it's simply time to adjust the spring tension on the voltage coil. On the military regulators, and some old civilian ones, you can turn a screw on each coil to adjust it, but on most of them, you bend the tang that the bottom end of the spring is hooked on. Away from the base means less spring tension and a lower output voltage, which is the way you want to go. Do it only a little at a time, and don't short your tool against anything while you're bending it.
If you push the arm of the voltage coil down, and you can clearly see that the points there are open, and yet the voltage remains high, some other thing is wrong that is causing full battery voltage to go the generator field. It could be a short elsewhere in the regulator, in the wiring, or in the generator itself. I'm almost certain, though, that manually opening the points on the voltage coil will drop your battery voltage down to 6.5 or less (6.3 nominal), at which point you'll know you don't have to hunt around for other problems, because the problem is in the regulator itself.
Under normal operation, with a charged battery, the points on the voltage coil should be vibrating slightly and you should see a continuous faint blue spark between them in dim light. The points on the current coil are similar, but they normally stay closed all the time, and only start to open when the regulator goes into current limit which normally only happens when the battery is very low. In your case, it's happening all the time, limiting at 35 amps, because the voltage coil is never saying "Enough!".
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