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Generator Problems '45 Farmall A

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thynes

10-08-2005 14:09:53




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I have a '45 Farmall A with messed up non-original wires. When I got the tractor the charging system did not work, and the wires were a cobbled up mess. Since they were goofed with, I don't have any confidence that the wires are correct.

I believe that I have a cutout relay, as it only has one coil. It has 3 terminals: gen, F, and Bat. I have found several wiring diagrams to help me out, but I still have some questions.

Question 1: On the cutout relay do I connect the "F" terminal to anything? The schematics I have show this with no connection. Inside the cutout relay the "F" terminal is connected to a resisitor. This resistor is connected to the ground of the cutout relay. It seems this "F" terminal is a redundant equilavent of the field resistor in the switch box, is this corrct? If that is correct then do I leave the "F" terminal unused?

Question 2: I had the tractor running for a while with nothing connected to the generator and noticed it was hot. I checked for voltage at, I think at the "A" terminal, and it was putting out voltage. When I reved the engine to full speed, the voltage went to about 30 volts. This voltage promptly burned out my 12v test bulb! Is this normal, or is there an internal short in the generator that is allowing output with no wires attached?

Regards, Tim

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Jim Becker

10-08-2005 19:28:38




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 Re: Generator Problems '45 Farmall A in reply to thynes, 10-08-2005 14:09:53  
Since it has only a single coil, it is a cut-out, not a regulator. It has an F terminal but normally isn't used if you have a light switch. So the answer to your first question is correct and unused.

The three brush generator can put out a fairly high voltage if no load is connected. The 3-brush generators are inherently current limited, not voltage limited. It shouldn't put much out if the field isn't connected. If you have anything wrong with the generator, it may be that the field terminal is shorted, which I wouldn't worry about.

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John T

10-08-2005 20:44:39




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 Re: Generator Problems '45 Farmall A in reply to Jim Becker, 10-08-2005 19:28:38  
Jim, can you tell me what the F terminal wires to inside a cutout relay?? Direct to ground or a resistive ground or what??? I havent had a Farmall in years but didnt rememeber using the relay for a Field path?? (Too many moons ago lol)

Thanks a lot,

John T



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Jim Becker

10-09-2005 11:27:52




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 Re: Generator Problems '45 Farmall A in reply to John T, 10-08-2005 20:44:39  
It is connected like thynes said in his first post. It is grounded through a resistor. If a tractor is equipped with a starter but no lights, there is no light switch to control the field circuit. The generator F terminal can be connected to the cutout F for low charge, or grounded to one of the cutout attaching screws for high charge. (And yes, connecting it that way is in the book.)



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thynes

10-08-2005 20:11:50




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 Re: Generator Problems '45 Farmall A in reply to Jim Becker, 10-08-2005 19:28:38  
Jim,

Thanks for the info.

How would I check for a shorted field coil?

You say not to worry if it is shorted, why so? Normally when something is shorted it isn't so swell...

Thanks again, Tim



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Jim Becker

10-09-2005 11:34:18




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 Re: Generator Problems '45 Farmall A in reply to thynes, 10-08-2005 20:11:50  
I was speculating that the generator F terminal, which should be insulated from the frame, may be grounded. Your comment that the generator produced a high voltage with F not connected led me to that thought. Grounding (even by a short) of the F terminal simply locks the generator into high charge. If the field had a short at the other (brush) end, it would be a problem and the generator wouldn't produce any output.

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John T

10-08-2005 16:22:39




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 Re: Generator Problems '45 Farmall A in reply to thynes, 10-08-2005 14:09:53  
Thynes, Ive not had all that much Farmall experience but I can tell ya this.

Your First question..... ..

If that "device" you call a cutout relay has 3 terminals labeled BAT and GEN and FLD,,,,, ,,sounds to me like its a full fledged Voltage Regulator instead of only a 2 wire Cutout Relay.

A Cutout Relay has but 2 terminals, labeled BAT and GEN. On those systems, the Generators Field post wired up to the light switch where it received a dead ground for High Charge but was grounded through a resistor for Low Charge. They DO NOT HAVE ANY CONNECTION TO OR FOR THE GENERATORS FIELD POST.

On Voltage Regulator Systems, they Wired BAT to the ammeters load side,,,,, ,GEN (or ARM) to the Gens Armature post,,,,,and FLD on the VR wired to the Gens Field post AND NOT UP TO THE LIGHT SWITCH.

Its possile they got converted over the years from a cutout relay to a VR ????? If you have a good working Gen and a good VR, I would use the VR instead of a light switch control !!!!! !!! i.e. wire the 3 terminals as stated above for a VR, NO WIRES TO THE LIGHT SWITCH

A Cutout Relay has but one coil/relay,,,,, ,a VR has 2 or 3 coil/relays depending on if it has current and voltage regulation. Why dont you take a good look at the labels on the terminals on the device you have and its insides again???


Second Question

If there were load on the Generators and there was no voltage or current regulation, the voltage could and should continually increase as the Gen turned faster and even pop a 12 volt light.

Post back your findings and any questions

Let me know if you need my complete Troubleshooting Procedure for non charging.

Good Luck n God Bless

John T

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