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Farmall M Electrical

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Aaron Smith

08-20-2001 05:55:04




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The ammeter on my Farmall M reads a negative amperage. When I rev the engine higher, it goes more negative. What's up with this? How can I fix it? Which manual will have an electrical schematic or pictures so I can check the wiring?




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JohnK

08-21-2001 05:36:51




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 Re: Farmall M Electrical in reply to Aaron Smith, 08-20-2001 05:55:04  
Aaron: I had a similar problem with my SA. I was told to reverse the field of my voltage regulator. I tried that, and it solved the problem! With the tractor running, take an insulated wire and touch the generator terminal, the one on the outboard side of the gen., to the top terminal of the vr on the side that has three terminals. Have someone observe the ampmeter as you do this. If that's the problem, the needle should jump over into the charge side of the meter. Also, are you sure that your generator is putting out enough charge?

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Aaron Smith

08-21-2001 06:05:55




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 Re: Re: Farmall M Electrical in reply to JohnK, 08-21-2001 05:36:51  
vr - voltage regulator? That's the little box on top of the generator?

So, if I am sitting on the drivers seat, there are two post on the generator, towards me from the regulator. On the regulator, there are two terminals on the right side, and one on the left. I don't recollect 3 terminals on one side. I assume the "outboard" side of the generator is the one that charges the battery?

When I rev the engine up to 3/4 throttle or so, it puts out around -8 amps on the meter.

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Aaron Smith

08-20-2001 07:37:59




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 Re: Farmall M Electrical in reply to Aaron Smith, 08-20-2001 05:55:04  

My negative terminal is grounded to the frame. Where can I get some pictures or diagrams on the correct wiring? The real problem is that my battery is not being charged during operation. I'll drive it around for a few hours, then shut down. It won't restart immediately after. I'll have to hook the charger up to it for a while.



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Bob M

08-20-2001 08:22:31




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 Re: Re: Farmall M Electrical in reply to Aaron Smith, 08-20-2001 07:37:59  
Aaron - What year is your M? Does it have a 3 postion (O-D-B) or 4 postion (L-H-D-B) light switch? Magneto or coil/distributor ignition? Post back and I'll try to help with a wiring diagram.



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Aaron Smith

08-21-2001 05:28:10




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 Re: Re: Re: Farmall M Electrical in reply to Bob M, 08-20-2001 08:22:31  
It has a 4-position light switch, and a coil/distributer ignition system.



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Bob M

08-21-2001 06:35:07




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 Re: Re: Re: Re: Farmall M Electrical in reply to Aaron Smith, 08-21-2001 05:28:10  
third party image

Aaron - This should be what you're looking for. It's from an A/B manual but your M will be wired identically. ...Bob M



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Aaron Smith

08-21-2001 09:17:07




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 Re: Re: Re: Re: Re: Farmall M Electrical in reply to Bob M, 08-21-2001 06:35:07  

Thanks for the pic. However, mine is wired with a negative ground. I can rewire to match your schematic, but what's the negative ground sketch look like, if you got it.

Also, what are the 4 switch positions on my light switch box for?



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The Red

08-21-2001 09:26:06




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 Re: Re: Re: Re: Re: Re: Farmall M Electrical in reply to Aaron Smith, 08-21-2001 09:17:07  
The 4 position switch is for low charge, high charge, dim lights, bright lights.

For negative ground using Bob's picture, swap the wires on the ampmeter and some folks swap the wires on the coil. Lights and starter don't care how you are wired up.



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Aaron Smith

08-20-2001 08:33:06




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 Re: Re: Re: Farmall M Electrical in reply to Bob M, 08-20-2001 08:22:31  
I'll have to check on the light switch when I go home tonight, I'm not sure of the year.



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The Red

08-20-2001 07:55:46




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 Re: Re: Farmall M Electrical in reply to Aaron Smith, 08-20-2001 07:37:59  
With it negative ground, the hot wire going from the starter switch to the light box should be on the ampmeter post that is opposite the negative indication on the gauge.

Clarify "It won't restart immediately after". Will the starter not crank or it is cranking and the engine is not starting?



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aaron smith

08-20-2001 08:24:35




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 Re: Re: Re: Farmall M Electrical in reply to The Red, 08-20-2001 07:55:46  
There is not enough charge in the battery to turn the starter.

I believe the hot wire from the starter is connected to the guage positive-side post. If my memory serves me right from this weekend. Positive gage post had 1 wire to it, and the negative gage post had 3 wires from it.



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The Red

08-20-2001 08:58:21




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 Re: Re: Re: Re: Farmall M Electrical in reply to aaron smith, 08-20-2001 08:24:35  
Aaron that would be correct for a positive ground hookup.



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Glenn(WV)

08-20-2001 07:30:15




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 Re: Farmall M Electrical in reply to Aaron Smith, 08-20-2001 05:55:04  
Sounds like the ammeter is hooked up backwards, but as Red says, it depends on whether or not you have positive or negative ground.



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The Red

08-20-2001 06:32:13




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 Re: Farmall M Electrical in reply to Aaron Smith, 08-20-2001 05:55:04  
Aaron are you positive or negative ground?



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