The Stovebolt Site Forums The Shop Area The Electrical Bay Generator cuts out at high engine speeds

Okay, enough time spent searching tons of informative stuff, but can't find my specific problem. I have put a '54 235 in a 1939 Chevy. I kept all the 6v electrics. My generator (worked on the 216) , works fine at low to mid engine speeds, ammeter indicates about half way charging, but goes way up to max, then cuts out if I speed things up.
At first, I had a bad ground on the gas gauge, which seemed to let the gen work again if I fooled with it. I fixed that, but still have the cutout.
If I repolarize, that sometimes makes the generator start again. Other times it just starts when I restart the truck. Could this be a regulator adjustment or high generator output (It reads 7.2 volts at a fast idle). I have checked grounds and connections, but this is a repeatable problem if I rev the engine or drive over 50. The battery shows fair on my Harbor Freight load tester and starts the supposedly rebuilt engine fine.
I have spare generators and can switch, but before I do, I would like any opinions on what would cause this.
I usually find anything I need to know at the Stovebolt, but I have not figured out how to make the search engine very specific.
Thanks for any ideas.

It is normal for the ammeter to go to the 0 charge when the battery is good & fully charged. If the volt meter stays at the normal charging rate when you rev it up, 7-7.5 volts you are good to go. Turn on the lights & heater. The amp gauge will go to discharge. Rev the engine & it should go to a charge & settle back to even. When the bat. is fully charged it has the same voltage as the charging system. There is no flow of amps back to the bat. It's like you have a tank with 50 lbs of air pressure. You put it to a tire & when the tire gets 50 lbs of air pressure there is no more flow. If the charging is falling off at high RPM's the belt may be loose.

As long as the voltage is staying above 7 volts against a fully-charged battery, you don't have a problem, even if the ammeter shows little or no charge. The battery is sort of like a bucket- - - - -starting the engine empties the bucket somewhat, and the generator refills it, with the ammeter showing a heavy charge. Once the bucket is full, all the generator is doing is supplying a relatively low current to run the igniton system, etc., with a very slow charge going to the battery. The next time you start, the current draw from the starter empties the bucket a little, and the generator goes back to a heavy charge for a short time. As long as battery terminal voltage does not drop below 6.5 volts, the generator is still charging, even with a very slight deflection of the ammeter needle. 7.2 to 7.5 volts against a fully-charged battery is better.
Jerry

Thank you for your insight. To use a common term "on further inspection" (Which I probably should have done before I asked), I think I have discovered my problem. The "stranded" wire to one of the generator brushes has become a "strand" wire. It was apparently rubbing on the rotor. It was either shorting at speed, or I suspect that it was carrying the generator load at low speeds, but not at high rpm? At least it looks like an easy fix to keep as a spare.
Thanks again for your information.