The Ford Barn

modelamodela · 06-05-2013, 08:58 AM

The generator on my 1931 puts out 20 amps, and moving the third brush doesn't reduce the output. What is the problem and how do you fix it? Thanks much

Patrick L. · 06-05-2013, 09:35 AM

What type cut-out are you using ?
Is the car correctly wired, especially a good clean correct battery ground?
It seems like the 'innerds' of the generator may be improperly wired. There are a couple recent posts regarding this and how to re-wire correctly.

Purdy Swoft · 06-05-2013, 09:53 AM

Usually if the brush wires are crossed, at first the generator will peg the ammeter . after running crossed for a while the charge rate will drop of to 3 or 4 amps and then quit charging at all and the field coils will be shot. If caught early and corrected it may be ok. If you have a new Brattons catalog, look at the left lower corner of page 66 for the internal wiring legend for the tube type generator. When adjusting the third brush doesn't change the rate of charge, the brush wires will usually be crossed. The generator will charge either way, just not for very long if crossed.

Mike V. Florida · 06-05-2013, 09:59 AM

Is the generator "new"?
What is the voltage at the battery with and without the car running?
Does it change when you turn on the headlamps and or blow horn?
Is your ampmeter working properly?

Tom Wesenberg · 06-05-2013, 05:45 PM

Is this generator new to you?
Did someone just work on it?
Was it working, and then this problem just started?

modelamodela · 06-10-2013, 09:01 AM

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The generator was working fine, but stopped charging, so it was replaced with another that worked OK.
Another Model A I have developed charging issues, so I pulled this one off the shelf and put it in, and now it does appear to be charging really high, sometimes it is at about 8 amps but as soon as the car is going 20+ MPH the rate is pegged at 20 amps. Moving the third brush does not change the charging rate.

sethkestenbaum · 06-10-2013, 11:00 AM

The generator shouldn't be giving you any positive charge at idle. Could you have a bad ammeter that is showing you more charge than you are actually generating? what does the ammeter read when the car is "on" but not running?

Tom Wesenberg · 06-10-2013, 01:36 PM

I would take the band off and make sure the two wires are connected to the right brushes. The field wire MUST be connected to the adjustable brush. The output wire must be connected to the insulated non adjustable brush. The third brush is not insulated and is the ground brush. There was a recent thread about a generator that just came from a generator shop and had the two brush wires crossed.

BTW, you should put a battery charger on the battery ASAP to bring it to full charge. I like to use a 6 amp charger for about 4 hours.

06-05-2013, 08:58 AM	#1
modelamodela Member Join Date: May 2010 Posts: 76	Generator Overchargeing The generator on my 1931 puts out 20 amps, and moving the third brush doesn't reduce the output. What is the problem and how do you fix it? Thanks much

06-05-2013, 09:35 AM	#2
Patrick L. Senior Member Join Date: May 2010 Location: Largo Florida Posts: 7,225	Re: Generator Overchargeing What type cut-out are you using ? Is the car correctly wired, especially a good clean correct battery ground? It seems like the 'innerds' of the generator may be improperly wired. There are a couple recent posts regarding this and how to re-wire correctly.

06-05-2013, 09:53 AM	#3
Purdy Swoft Senior Member Join Date: May 2010 Location: Alabama Posts: 8,099	Re: Generator Overchargeing Usually if the brush wires are crossed, at first the generator will peg the ammeter . after running crossed for a while the charge rate will drop of to 3 or 4 amps and then quit charging at all and the field coils will be shot. If caught early and corrected it may be ok. If you have a new Brattons catalog, look at the left lower corner of page 66 for the internal wiring legend for the tube type generator. When adjusting the third brush doesn't change the rate of charge, the brush wires will usually be crossed. The generator will charge either way, just not for very long if crossed.

06-05-2013, 09:59 AM	#4
Mike V. Florida Senior Member Join Date: May 2010 Location: South Florida Posts: 14,054	Re: Generator Overchargeing Is the generator "new"? What is the voltage at the battery with and without the car running? Does it change when you turn on the headlamps and or blow horn? Is your ampmeter working properly? __________________ What's right about America is that although we have a mess of problems, we have great capacity - intellect and resources - to do some thing about them. - Henry Ford II

06-05-2013, 05:45 PM	#5
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Generator Overchargeing Is this generator new to you? Did someone just work on it? Was it working, and then this problem just started?

06-10-2013, 09:01 AM	#6
modelamodela Member Join Date: May 2010 Posts: 76	Re: Generator Overchargeing Sponsored Links (Register now to hide all advertisements) The generator was working fine, but stopped charging, so it was replaced with another that worked OK. Another Model A I have developed charging issues, so I pulled this one off the shelf and put it in, and now it does appear to be charging really high, sometimes it is at about 8 amps but as soon as the car is going 20+ MPH the rate is pegged at 20 amps. Moving the third brush does not change the charging rate.

06-10-2013, 11:00 AM	#7
sethkestenbaum Senior Member Join Date: Jun 2011 Location: Westchester County, NY Posts: 632	Re: Generator Overchargeing The generator shouldn't be giving you any positive charge at idle. Could you have a bad ammeter that is showing you more charge than you are actually generating? what does the ammeter read when the car is "on" but not running? __________________ Seth Kestenbaum www.oldcarroadtrip.com

06-10-2013, 01:36 PM	#8
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Generator Overchargeing I would take the band off and make sure the two wires are connected to the right brushes. The field wire MUST be connected to the adjustable brush. The output wire must be connected to the insulated non adjustable brush. The third brush is not insulated and is the ground brush. There was a recent thread about a generator that just came from a generator shop and had the two brush wires crossed. BTW, you should put a battery charger on the battery ASAP to bring it to full charge. I like to use a 6 amp charger for about 4 hours.