VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 Generator over charging

I just rebuilt my generator, placing new fields in the body. Upon starting thr car, it apears that it is over charging. I have moved the third brush, but he amp meter still pegs at 20 amps while driving. Could the cut out switch cause this? Confused.

More info, at idle, it's around -10 amps with headlights on, at cruzing speed it about 20 amps or more (lights on). I fear that if the lights weren't on I would blow out a wire somewhere.

Hi 3rdowner,

The cutout will not lead to the overcharging. Its only function is to disconnect the generator from the battery and electrical system when the generator output drops below a certain level, like when it is not running. Have you moved the third brush in the right direction - away from the insulated brush? Moving the third brush in the direction opposite to the rotation of the armature (ie towards the motor) will reduce the generator output. Overcharging like you're reporting can lead to more than just a blown wire. Try a blown battery! We're talking a full blown explosion - splitting out all the side seams and blowing off the top. As one of the other contributors to this site says, ask me how I know.

Happy Motoring,

Dan

Thanks Dan, I do fear an explosion of the battery. I did move the third brush, and with lights on, at speed, it pegs out at 20 amps. Could a short cause this? My education tells me no, because when I load the system (I.e. lights on) the meter goes discharge at idle. A short should act like a load. I wired the third brush to the output wire, that should be correct, right?

What year car are you working on?

The third brush should be wired to the field coil and the main brush should be wired to the "Gen" terminal on the cutout. Depending upon the generator model (what is your model number?) when the third brush and the main brush are four comm. bars apart (the third brush is towards the engine and away from the main brush) the generator should put out about 12 amps max. at speed with the lights off.

Junkyard,

The gen has the following numbers on it: 943B. 949g80

I may have it wired wrong. Please let me know what you find

Thanks

Junkyard,
My father and grandad operated an auto repair biz back in the late 20s and 30s. Dad's experiences led him to believe that it was best to 'error' on the side of undercharging with cutout relay only systems then periodically trickle charge overnight to bring it up to full charge (hydrometer determined). This supposedly extended battery life, especially when these cars were used on a daily basis. There was some controversy at the time with a belief that you would irreversibly 'sulfate the battery' by not always keeping it at full charge. Battery technology has probably improved since then but for the benefit of those of us running the oldies on an occasional basis ( but with 400 miles of touring sometimes) what is your advice on this issue?
Dan

Very interesting.....My Opinion Is our fathers and grandfathers learned from experience and they tried to pass it down to us to the best of their knowledge.We should take that serious until proved otherwise.....ED

Model 943 B fits 1926-28.



I agree. That's pretty much what I do on my 1932 and it seems to work great.

1926 was the first year for the 943-B model generator,albeit a "REMY" brand.

End of story, I change the wires between the third brush and the field brush and everything is fine, with the generator that is. See my next post for the new situation....

Gotta love these old cars!!!!

I try to set my generators on 4 bangers and early 6s to 6-8 amps. At that it is still necessary to occasionally run with the headlights on during the day to keep from boiling the battery.

I also have a three brush generator with electronic regulator in the band (bought many years ago from Jim Peterson) that in most cases gets switched between the vehicles I take on tours. It is set at max. amps and only runs at > 12 amps for a minute or two after starting. Quickly drops to slightly positive (on ammeter) and stays there. Made me realize how little power is required to start these old Chevys.

I set them up so that they are making 0 to 1 amp with the headlights on. That gives something like 8 amps with the lights off and seems to work well because I've never had a problem in service.

Regards
Al

Could someone expand on how to adjust the third brush to reduce the charging amps? Do you have to remove the generator from the car? Do you have to take the generator apart to adjust? Our '28 Chevy is charging about 12-15 amps without lights on. I need to get it down much lower.

Thanks,

David

Loosen slotted screw on back of generator and then move brush one way is higher other is lower.Al

Check out your shop manual....it will tell you in detail how to do it.

After you loosen the round head screw on the back of the generator (do not remove the screw), move the third brush towards the engine to decrease the generator output. If you move the third brush towards the fender it will increase the generator output. The above is done with the generator in place on the car.

A nice pictorial view on adjusting the third brush from Bill Barker's 1931 Chevrolet site:

http://1931chevrolet.com/specs11.htm

Happy Motoring,

Dan

That is a good illustration. I think it would have been better to illustrate a decrease in output instead of increase as that is what most generators need. Thinking people will figure it out.

Just for peoples info.
A mate of mine does a lot of miles in his 29 tourer, has done over 50,000, and he has welded a T bracket to the adjusting screw for easy adjustment. He's also placed a mark on the back of the generator showing DAY and NIGHT. The toggle makes for an easy adjustment.
Chris