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So I changed to 12 volt generator and everything seemed fine. Now it's only putting out 12.25 to 12.4 with or without load. Seems low. It was putting out 13^. I'm thinking voltage regulator is to blame. So what amp voltage regulator. There are several listed 20,35,50
Thanks for any insight.

What condition is the battery in? A generator will only put out enough voltage to push a charge into the battery. A discharged battery will accept a charge at a very low voltage until it begins to recharge, and the voltage will gradually rise until it reaches the voltage regulator setting. That's usually 14.5-14.7 volts AGAINST A FULLY CHARGED BATTERY! You also need an accurate ammeter to check out a charging system. Ths dash ammeter IS NOT, and never will be sufficient to check generator output. You MUST know volts and amps, plus the state of charge of the battery, to check a charging system properly.

Connect a jumper wire from the generator F terminal to ground. That will put the generator into full voltage output. DO NOT rev the engine much above a fast idle with the field terminal grounded.

Jerry

All I can tell you is that my generator/regulator combo will run at 14 volts in cold weather no load, when the engine/regulator warm up the voltage drops to about 13.5. If I'm driving at 2000 rpm or above, it will handle the heater and lights at 13.0 - 13.5 volts. Delco Remy genny and regulator that were on the truck when I acquired it 8 years ago.

Brand new battery. Charged up before installing. It worked great for a day. Amp gauge shows discharge with heater or light on. Multi meter shows 12^ still. Amp gauge was jumping up to charge as it did with the 6 volt system but now it's not. Cleaned points in VR with paper but no change. I have the alternator stuff almost ready but this is baffling me.

I'll try the full field trick tomorrow. Do I not need to unhook the field wire from VR first? Or just ground it with wires still connected ?

Well this morning went out and started the truck. Still not charging. Then all of a sudden wahala amp gauge swings to charge. Multi meter shows 13.62. What the heck. Have a new VR coming this afternoon. Standard brand supposedly made in USA. That's what I have now so warranted.

Fixed for now anyway. New voltage regulator is working. FYI stamped made in USA. Standard part number VR20

Did you remember to polarize the generator after installing it? With all the wires connected, momentarily connect a jumper wire between the BAT and ARM terminals of the regulator (1/2 second or so). You'll get a pretty good flash- - -that's normal. Engine running or stopped doesn't matter. Flashing the circuit creates "residual magnetism" in the generator field coils which is needed to start the charging process when the generator starts spinning.

A properly polarized generator will show 1/2-3/4 volts at the armature terminal with no wires connected, and the generator spinning at idle speed.
Jerry

Yes sir Jerry. I took the cover off the old one and I think the problem was the points at the battery terminal were crooked and pretty wide. But got it warranted so hopefully the new one will keep working. Thanks for all your input.

I was fortunate enough to learn how to rebuild and adjust regulators, back in the late 1950s when generator/regulator systems were just beginning to be phased out in favor of alternators. They're not that difficult to repair, but most "mechanics" who have entered the trade since the 1970's don't have a clue how either generators or regtulators actually work, or how to do the checks and adjustments necessary to keep them working properly.
Jerry