47-55.1 Generator Issue

[JoeDude]

I have a 12v generator. It shows about 13v at say, 1,000 revs or so but only 9v at idle. Also, the amp gauge does not move from center until I turn the lights on, then it goes to the discharge side. Is it possible I hooked the generator wires backwards?

[mr48chev]

The bad thing about generators from day one has been that at an idle they don't put out much if any charge and need an engine speed of 1500 or up to actually charge. That is just the way that they have been since day one that they were used on cars and trucks be they a 6 volt or 12 volt or ??

This is how a Delco generator should be hooked up. After I got back I didn't like the way they hooked up the alternator in place of a generator in case you wonder where the other half of the picture went.

Note how the generator is wired to the regulator. check your wiring.


The thing with a generator when you put it on a rig for the first time is that you almost always have to "polarize" it to have it work right. I don't have time right now to write instructions on how to do that right and will have to go get my notes out of the garage to copy or photograph and post. They can be found online in the OLD car manuals though. Just look in 56/61 Chevy truck manuals. After I get done hauling my wife to the store (s) and getting chores done I'll try to remember to get the book out and get the instructions .

YOU ABSOLUTELY DO NOT POLARIZE AN ALTERNATOR though. I learned to rebuild alternators in the 60's because old farts would replace one on their car and try to polarize it and blow the diodes out.

[Hcb3200]

MR48 is referring to this manual

https://chevy.oldcarmanualproject.co...M300/index.htm
Look at Page 11

It has what you need to review that generator and how to polarize.

[dsraven]

if you cant get it to charge or need to rebuild it or replace parts you may want to look at swapping it for an alternator. they charge better and probably have more output. if you have more than lights and a fan operating the generator is gonna be overtaxed likely. an altenator will keep up better. if you are going with a numbers matching redo or want a totally stock truck then it will be what it is. adequate if bone stock and operating properly.
here isa thread on the alternator swap and how it's wired. I did a swap on a buddies '54 and he hasn't looked back. waaay better.
https://67-72chevytrucks.com/vboard/...d.php?t=783739

and another

https://smithcoelectric.com/blogs/te...wiring-diagram

and one on polarizing the gm generator from that era

https://www.motortrend.com/features/...962-corvettes/

hope that helps

[mr48chev]

I'm gong to assume that JoeDude wants a generator to keep the engine compartment looking original and don't have an issue with that as long as he understands that generators don't and never have work/worked like an alternator does and you have to expect the lights to dim at an idle or low speed and if you put pup around cruising at night with the lights and radio on you can actually drain the batter with every thing working right. They just flat are not going to charge much at low speeds. That's the price of being one of the cool guys.

As far as wiring diagrams for installing alternators i keep every one I find that I believe will actually work here. https://photobucket.com/u/mr48chev/a...6-e6e6bd785eac