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1949 AC G electrical

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02-20-2002 11:29:24

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My 1949 AC G tractor has a cutout relay. I know it's a dumb question BUT, what's it used for? Is it used in place of a voltage regulator? How is it wired into the charging system?

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02-20-2002 14:04:14

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 Re: 1949 AC G electrical in reply to oldaggie, 02-20-2002 11:29:24  
The cutout relay opens the circuit between the battery and the generator when the voltage being produced by the generator is less than the voltage of the battery (i.e when the tractor is shut off or idling). If the relay was not used, the battery would discharge through the generator when the tractor is not running. In fact, if you apply voltage to the armature terminal of the generator it will run just like an electric motor. A voltage regulator has a cutout relay built into it. On the G and other old tractor charging systems, they do not have a voltage regulator, the charging rate being controlled by the resistor built into the light switch, so they just have the small cutout relay. The relay is nothing but an electromagnet that pulls a set of points closed when the voltage produced by the generator gets to a prest level. If I remember correctly, on a 6 volt system, the points close and it will start to charge when the generator is putting out 7.2 volts. If you watch your ammeter when you slow the engine down on your tractor, you will notice it go into discharge for just a moment then jump up to 0...this is when the points of the cutout open.

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02-20-2002 15:08:53

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 Re: Re: 1949 AC G electrical in reply to DanD., 02-20-2002 14:04:14  
Thanks. That was a good explanation. Even I understood it.

I bought this tractor last Summer but put it aside until a few days ago. Today I noticed that the wiring was inconsistent with that shown in the Owners Manual. So, I re-wired it to make it consistent with the manual. However, when I tried to start it, smoke started coming from the starter terminal. So, I disconnected the battery. About 30 minutes ago, while looking at the manual again, I noticed that it is a positive ground system. Whoever had the tractor before me changed it over to negative ground wiring and connected the battery negative post to ground. I suppose that is why the wiring was inconsistent with the manual. It ran fine as it was wired but the ammeter was bypassed so I couldn't tell if it was charging. Also, the armature terminal of the generator was not connected to anything.

Tomorrow I will connect the postive battery terminal to ground and hope everything works. Thanks again.

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02-20-2002 19:11:50

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 Re: Re: Re: 1949 AC G electrical in reply to oldaggie, 02-20-2002 15:08:53  
you can run the tractor with positive or negative ground as you noted. the starter and lights will not know the difference. as you also noticed, the tractor came with positive ground and that is how the generator works. if you run negative ground you must disconnect the generator "A" terminal as it is trying to charge "backwards". The "A" terminal goes to the cutout, then the amp meter, then charges the negative battery terminal.

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02-20-2002 19:13:46

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 Re: Re: Re: Re: 1949 AC G electrical in reply to steve, 02-20-2002 19:11:50  
I hope you have a 6 volt battery?? If it is 12 volt, that is why they removed the generator from service and connected the tractor as negative ground.

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