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I finally got the electrical system powered up for the first time on my project truck today. It's a '49 that I've converted to 12V negative ground. I'm using a 12V Delco generator and regulator. The thing won't charge. With the belt loosened, I quickly jumped from the battery to the armature in an attempt to polarize the generator. It spun just like I'd expect it to, but opposite of normal rotation. Does that sound right? Everything else is wired correctly. On the regulator I've got 12V+ to BATT, A on the gen to ARM on the reg, F on the gen to FLD on the reg. All the connections are clean and tight.
What do I check next?

Check your back account and see if can buy an alternator. No reason to stay with a cumbersome, wire encumbered, dinosaur dynamo. Too many failure points.

The truck is a period correct resto-mod so I'm sticking the generator. An alternator would look terrible on a hot rodded 235. It's got to be something simple I'm overlooking

Here's some literature for you:
http://www.navioneer.org/riprelay/The%20Navion%20Files/delco_remy_regulators.pdf

http://www.navioneer.org/riprelay/The%20Navion%20Files/Delco_Old_Generators.pdf

A resto mod hot rod has to have a generator. I did not know that. Sounds good. Hot Rod Jerry will be along to troubleshoot your difficulty. He knows them electrics.

If the generator will "motor" (either direction) it will also charge. Try disconnecting both wires (armature and field) at the generator, and running the engine at idle. A DC voltmeter should be able to measure at least 0.5 volts between the armature terminal of the generator and ground at the housing. ("residual voltage"). If that is there, the next test will be to attach a jumper wire from the "field" terminal of the generator to ground at the generator housing. With the field grounded (still no wires attached) the armature voltage should rise dramatically- - - -maybe 20 volts or more as the speed is increased. If the generator passes these tests, it's good. I'm going to guess your problem is either in the wiring harness between the generator and the regulator, internal problems inside the regulator, or a bad ground between the regulator base and the generator housing.

Drop me a PM, and let's have a phone conversation. I can share more test procedures in a 15-minute phone call than with a novel's worth of typing.
Jerry

The guru has spoken. Listen closely, and slowly. (He is from Tennessee. He talks slow. )

Sound like the OP needs one of these:


https://www.qualitypowerauto.com/item_543/6-Volt-GM-Positive-Ground.htm


The link is 6 v.........They sell 12v alternator that look like a generator.

Not for $500!! I've heard those things are notoriously unreliable as well

RUN- - - - -do not walk away from that fake generator! There's a reason alternators are short and large diameter- - - - -the physics of creating alternating current doesn't work right in a long, skinny housing. An alternator creates 3 phase AC current from the stationary stator windings in the outer housing, and then rectifies it into a fairly stable DC flow with six heavy duty diodes. A generator creates a pulsating DC from the spinning armature, thanks to the commutator bars at the end of the armature.
Jerry

Well, I think the field is bad. With the truck running and voltmeter connected, I grounded the field and got exactly 0V....

Did you have any residual voltage? If there's no voltage at the armature terminal there won't be anything to kick off the field current when it's grounded. Try checking from F to A with an ohmmeter with the wires disconnected- - - - -you should get a reading somewhere in the 5-10 ohm range. Also, try polarizing again, this time without letting the pulley spin. Apply battery voltage to the armature terminal for a second or so. You'll get a pretty good flash, but that won't hurt anything for a short time.
Jerry

Jerry, can a 12V generator be set-up to "motor" during a bench test? If so, what connections are necessary? I have a 12V generator I'd like to test.

Thanks,

I usually ground the F terminal to the generator housing and apply battery voltage to the ARM terminal while the generator is clamped in a vise. Connect the battery ground to the housing, or just clamp the end of a cable under the vise jaw that's holding the generator. Sometimes it's necessary to give the pulley a little spin to get things started. Don't run one long that way (15 seconds or so is plenty), as it can overheat the windings.
Jerry

Here is a novel concept for you. One wire (plus the battery cable) replaces all your charging wiring mess, no separate voltage regulator, no testing, no reverse rotation, no polarizing, smaller, easy in stall, no shame, no fiddle, no diddle, no kidding. AC Delco.....43 bucks. Puts the "mod" in restomod.

"AC Delco.....43 bucks" plus a $25 core charge.

However, it does indeed look like "no muss; no fuss" installation (and the price with core charge is not bad).

It would be nice to hear back from someone on this one?

Nice find, bartamos

Didn't see that. Didn't shop around like I would if I was buying. Here are some with lower core/lower total price. There are 100's of them for sale on the web. Just wanted to remind those who are shifting to 12V and doing some modernization. I believe this is a priority good thing to do.

I am of the opinion that buying one that says AC Delco does not mean much as far as rebuilt. Probably only one or two rebuilders feeding these venders. All using the same case. If it's "new", it's a Chinese casting permitted by whomever owns the design using "relaxed specs". If it's rebuilt, it could have a good old USA Delco casting or a Chinese casting.

The subcontractor for GM's ACDelco branded parts is the country of China. They are as good as it gets because that's all you gets. Buy them for $165 at a boutique or $29 at Rockauto. Same exact unknown reliability. As with anything now-a-days.

The diodes that build the rectifier are Chinese, the bearings/bushings are Chinese, the pulley is Chinese, the windings, Chinese. The person who builds or rebuilds is Chinese, the ship that brings it to the USA is a Chinese owned boat with a multinational crew, none of which are Chinese. They would defect.

Pretty good cop-out for people who lack the patience, intelligence, or skill to make a DC generator work. I'm amazed we won WW II with generator-equipped trucks, tanks, and airplanes!
Jerry

Jerry, You make me laugh with every post!
And you are right! DC generators are very simple machines.

Don

I like it when my headlights dim down automatically at idle!

Ok, so I re-polarized the generator. With everything disconnected and the engine running at idle, I'm reading negative .55V between the armature and housing. Yes, negative and yes, I had the meter hooked up the right way. When I ground the field terminal nothing changes. I'm thinking my generator needs a visit to the shop....

Post the sequence of steps you followed when you polarize the generator, please.

12v negative ground system - correct?

Yes, if you can't raise the voltage with the field grounded after re-polarizing, there's an internal problem with the generator- - - -possibly a bad armature or an open field winding. Can you see the brushes? Sometimes just sanding the armature where the brushes ride and installing a new set of brushes can "wake the dead"
Good luck!
Jerry

Reach in with a finger nail, pull back the springs which hold the brushes against the commutator and let them snap into place.
I had one that stopped charging midway of a 1,000 mile trip. I did just that and it started charging. I put 15,000 miles on that truck after that before I parked it for 18 years. After that 18 years, I charged the battery, and cleaned the points. It started up and purred like it always did and the ammeter showed a charge.
Dirt must have bound up the brushes. Once the brushes wore just enough to not make contact, it stopped charging.
Carl

So, the mystery has been solved. I brought the generator to the old-timey electric repair shop. The nearly 90 year old owner immediately spotted the problem. It's a counter clockwise generator. How the hell I ended up with that I'll never know. Anyway, he said it's real simple to switch the field windings to make it clockwise and he'll have it done tomorrow. Score.

He's probably going to swap the back end frame for one with the brushes in a different location. There's a definite geometry difference between the ones that turn CCW from the drive end and the armature windings that affect where the brushes need to contact the commutator bars. Thank goodness for old geezers!
Jerry

Hail to old geezers!
I have recently noticed that I have begun geezing more and more frequently lately. Cranky too.

Where would a CCW generator be found / used? Not that I pay that much attention, I did not know that there was a difference and application for both.
Maybe in the southern hemisphere where the world spins in different direction?

Probably some sort of industrial/commercial engine application. I remember a 64 Freightliner I maintained many years ago that had an alternator driven from the rear gear case of an 8V-71 Detroit Diesel engine, and it was CCW rotation. That wasn't a problem, as I'm pretty sure alternators will spin in either direction and give the same output, other than possibly needing a different style of cooling fan.
Jerry

Some marine engines also run CCW

Good to know. Thanks for insight.

I picked up the revised generator today and got it installed. It charges like a champ, 14.3V at high idle. I did get the opportunity to see it in action on the 1950's SUN test machine before I brought it home and it did almost 50 amps. I'm impressed...

Jerry,

Your generator test worked like a charm! It took off on its own and I ran it for 10 seconds or so.

Thanks,