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Trying to determine why my ammeter never reads charge, I checked the contacts on the cut-out and they don't close at any engine speed. I closed them by hand for a moment with the engine idling, and while revving, but the ammeter only registered a very slight discharge regardless. I figured the third brush might not be turned up enough so I took off the generator end cap. See photo.

The third brush is at the top and is adjusted by loosening the small hex bolt and turning the striated cylinder underneath it. What puzzles me is why the braided copper wire from the third brush appears to be grounded to the generator body beneath the screw adjacent to it along with another wire, which I assume goes to the field windings.

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I don't know where this schematic came from -- maybe O_D posted it?? -- but believe it may work for the question you have about the third brush being grounded and where the field wire goes.

Perhaps there is more than one version of that generator because this one doesn't look like the third brush should be grounded. The way it looks, depending on where it is positioned the third brush is picking up a higher or lower supply voltage for the field and if it is grounded there would be no field voltage and no charging other than what could be provided by the residual magnetism of the field poles.

Didn't someone mention some Owen Dyneto generators with the third brush could be and were modified to eliminate the brush control and run a different or modern style regulator? Maybe that is what was supposed to happen and was done incorrectly.

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Didn't someone mention some Owen Dyneto generators with the third brush could be and were modified to eliminate the brush control and run a different or modern style regulator?

There are several services out there that can modify any 3rd brush generator, not just O-D units, to run with a modern 3-pole regulator or even a solid state regulator.

Sherlock, what is your generator number?

Re: "Adjustable 3rd brush grounded"

I'm not real familiar with OD generator. BUT BE ADVISED that ANY generator from ANY application may have been modified over the years to acomodate variations in availability of parts.

Some gens are FIELD ground regulation and some are ARMATUER ground regulations depending upon OEM designs that can vary from MFG'er to Mfg'er.

Therfore, regardless of OEM design then ANY gen from ANY application may have been modified over the years simply due to NEED or parts availability at any given time.

Therfore, u will need to do some indepth study on this issue.

Hi all and thanks for your replies.

Dave, the generator is a CG 697. No Packard used that model to my knowledge. I was able to ascertain that the model was used on a 1927 Franklin and probably other makes, so it must've been a junkyard fix. Because of the early date, I would think this model was intended for use with a cut-out only like Packards of the same vintage. As you know, Packard didn't use external field regulation until 1930 when a simple external field regulator was employed to function in addition to the third brush. I doubt other makes were much more advanced.

I considered the possibility of later alteration, but any alteration for a more modern regulator would require a wire from one end of the field windings exit the generator case, along with the wire that supplies current to the battery. There is only one wire exiting my generator case, and that comes from a main brush.

The wiring as it is would make sense if the screw attaching the braided third brush lead and the other lead (that I assume goes to the field coils) was insulated from the generator body instead of grounded to it. In that case the far end of the other lead should be grounded to the generator body. I believe I'll do a continuity test to verify where precisely that other lead goes. The ohmmeter should show current flowing with a fairly high resistance owing to passing through the field coils.

Here is a generator schematic with no external field regulation.

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Interesting, Howard. In the diagram there is a fuse in the field circuit. I wonder if originally there was a fuse holder of some sort connecting the braided lead from the third brush with the field wire. The screw may have been intended to fasten the holder instead of grounding both wires. I've read generators that used a simple cut-out always had such a fuse inside the generator (instead of in the voltage regulator like later systems). It's intended to prevent the generator from burning out in case of an open circuit to the battery, which could easily happen. I was puzzled when I couldn't find a fuse in my generator.

It appears that the Franklin 11B (1927) was the only make of US car to use the CG 697.

So it must be fairly rare. Dave, do you happen to have a wiring diagram or other information on this model? I'm particularly interested in the type and location of the fuse.

Unless I have something I've forgotten about, my oldest is Edition T of the Automotive Electricians Manual which has some data and listings to the mid 1920s but the earliest wiring diagrams are 1930. I'll call some friends and see if I can find something earlier.

PS: Franklin 1927 production about 8100 units so yes, I'd say it's a pretty rare generator. I'll bet that somewhere there's a Franklin owner who'd love to have it.