Farmall wiring

I have an old Farmall 300 that I have converted to 12v but recently there have been issues. I am not sure the charging from the alternator is working correctly. I have an ammeter and sometimes it shows a strong move to the right and then just a slight move. This seems normal but not quite. (Bit confused there right?) Putting a volt meter on the battery shows steady change in the voltage that I am receiving. It goes very quickly from 14v to 16v to 8v and all over the board. Am I looking at a bad voltage regulator in the 10si alternator that I am using. Has anyone seen this jumping voltage issue? I depend on this tractor. Thanks for any assistance anyone can provide.

 

You should not have a voltage regulator except for the one that is internal to the alternator. The VR you have may still be the 6v. one. The ammeter is also probably 6v and is only giving you half the amperage you should be seeing. I would opt for a more modern volt meter to assess the condition of the battery charge. How 'bout headlights? Did you change them to 12v as well or are you using a voltage resistor block to reduce the voltage? Did you match the pulley of the alternator to the one off your generator?
I converted my old 1942 9N many years ago, and the Ford 640 I drive now. Yeah, you get to depend on these old babies and when they go down, they go down hard.

 

It was converted a couple of years ago. Everything is 12volt. No resister and same sized pulley. There is no external voltage regulator but just the one inside the 10si alternator.

 

Well alrighty then. You said you had a steady change in voltage on your external volt meter. Then you say it jumps voltage values erratically. Is this shown on your meter, too? How fast is the engine running? Sometimes I get fluctuations in voltage at idle, until I put a load like headlights on it, then it pops up to 14 volts, because it sees a demand. Higher speeds seems to calm it all down.
I'd hate to do it, but if all the above doesn't check out, pull the alternator and have it bench tested. Hey, it's easier than pulling one off a Corvette, huh??

 

True, it does come off easily. At normal idle speed, maybe 750 to 1000 rpm, the voltage meter hooked to the battery jumps all over and does so even with the lights on. The ammeter does not jump at all. If I didn't put the volt meter on the battery and went from the ammeter I would think things looked good. Maybe I will wait and see how things go. I have another 10si. Would you know how to bench test the thing?