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Farmall & IHC Tractors Discussion Forum
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Positive Ground

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Orion

12-06-2004 13:43:37




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I have a farmall M. This weekend, I was replacing the starter switch and, as I pulled the battery box and battery, I noticed that my ground is actually hooked to the negative of the battery and the starter wire is hooked to the positive. This tractor has long ago been converted to 12 volt with a 12 volt generator. My question is two-fold. First, is it normal for a 12 volt conversion to end up with a negative ground? Also, if my cables are reversed, would it even work, or would it damage my electrical system? Thanks

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gusc

12-07-2004 15:13:59




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 Re: Positive Ground in reply to Orion, 12-06-2004 13:43:37  
Your tractor doesn't care if it is neg or pos ground nor does your starter or gen just as long as you polarize the gen and reg before starting the engine.

Nothing else will be affected except the ammeter may read in reverse and the coil wires being reversed may cause a small decrease in power which you won't be able to notice.



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willie j

12-07-2004 04:24:32




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 Re: Positive Ground in reply to Orion, 12-06-2004 13:43:37  
Somewhat OT. 61 Falcon car, 12v gen, supposed to be neg ground, electrically challenged neighbor. He put in points & plugs, asked me to check timing. Hook light's red clip to batt hot post, black clip to engine ground. Light doesn't work. Hooked light to my car to check, worked ok. Recheck set up, batt was in pos ground. Switched batt cables, everything worked, radio even came on at full blast. Checked install date on batt, was there over a year, same time the radio quit. Maybe just dumb luck, but seems the gen/reg reversed itself when the batt was put in bassackwards.
Also worked part time at a gas station repairing generators. Turn armature, bearings, brushes etc. Ford was the only one we had to polarize. GM, Chrysler,& IH just hook up, start up & drive away. Never had a do-over recall. Willie J

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Doug in OR

12-07-2004 06:27:39




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 Re: Positive Ground in reply to willie j, 12-07-2004 04:24:32  
It was not unusual for some tractors to have positive ground for a short initially after the manufacturers converted to 12 volts. With a generator, you can do it either way. Negative ground is a must if you are using a standard alternator, though. Negative ground also has an advantage if you are adding electrical equipment, such as a radio, that is grounded internally and requires a positive feed to that equipment.

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Geoff NY

12-06-2004 20:35:51




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 Re: Positive Ground in reply to Orion, 12-06-2004 13:43:37  
Agree with some of the info given, however do not assume that all 12 volts are neg ground. All the IHC diesels were 12 volt positive ground back in the day.



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mattd

12-06-2004 19:20:55




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 Re: Positive Ground in reply to Orion, 12-06-2004 13:43:37  
i think the positive and negative posts on the battery are slightly different sizes. im not sure which is wider off the top of my head but i think they are. so if youre cables are right theres only one way to hook it up.



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Martin

12-06-2004 15:51:46




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 Re: Positive Ground in reply to Orion, 12-06-2004 13:43:37  
So, just curiously, if I hooked a battery onto my A backwards to make it positive ground which I'm prettey sure it was originally, would I be able to start the engine without a problem? I'm not sure, but if my memory serves me right from back in the fifth grade, it you reverse polarity to a motor, the motor turns the other direction...



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Novel Idea Guy

12-07-2004 08:47:08




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 Re: Positive Ground in reply to Martin, 12-06-2004 15:51:46  
If the starter were a conventional motor, then yes, it would turn the opposite direction.

The starter has no permanent magnets. The motor is what I believe they call "shunt wound," so if you reverse the polarity, you reverse it for both the rotor and stator, and the motor ends up turning in the same direction.



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captaink

12-07-2004 07:06:06




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 Re: Positive Ground in reply to Martin, 12-06-2004 15:51:46  
No, the starter rotation is not based on battery polarity. I remember changing the rotation of a starter once for a special application, but not positive off hand how I did it. Seems to me I changed the ground brush to be the one attached to the fields and vice versa, but that was a long time ago.



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CNKS

12-06-2004 17:36:11




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 Re: Positive Ground in reply to Martin, 12-06-2004 15:51:46  
The starter will turn the same way, but you will eventually fry your voltage regulator. The starter does not care how it's hooked up.



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Martin

12-06-2004 18:19:14




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 Re: Positive Ground in reply to CNKS, 12-06-2004 17:36:11  
I see, I don't have anything other than a starter that is electrical, but that will make finding certain parts easier!



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CNKS

12-06-2004 14:10:26




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 Re: Positive Ground in reply to Orion, 12-06-2004 13:43:37  
If it is working fine, don't change it. The only potential problem is the regulator. The OEM 6 volt regulators were intended to be used only with positive ground. Not sure about the 12 V ones. If it makes a difference it will be marked on the regulator, possibly on the underside. If you see no markings, leave it alone.



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captaink

12-06-2004 13:51:06




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 Re: Positive Ground in reply to Orion, 12-06-2004 13:43:37  
Positive ground is common for 6-volt systems and negative ground is common for 12-volt systems. The starter doesn't care about polarity. The ammeter needs to have wires reversed so that it indicates charge/discharge correctly, otherwise it doesn't care either. Generators and voltage regulators need to be polarized to the system, but alternators are real fussy about needing negative ground polarity along with any other goodies such as radios that you might consider adding on.

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Andy Martin

12-06-2004 15:02:10




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 Re: Positive Ground in reply to captaink, 12-06-2004 13:51:06  
If you're lazy like me, and you have a couple of 12v neg ground tractors with polarity reversed on the ammeter, you get used to that good feeling of the needle going far left as soon as you start up.



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captaink

12-07-2004 06:39:29




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 Re: Positive Ground in reply to Andy Martin, 12-06-2004 15:02:10  
Some people's kids...sheesh! You buy them books, glasses, and send them to school and what do you get? Evidently you must like to keep strangers on your tractors confused and worried… :>)



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Andy Martin

12-07-2004 14:38:50




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 Re: Positive Ground in reply to captaink, 12-07-2004 06:39:29  
Strangers on my tractors?

Maybe on my wife but never my tractors.



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rustyfarmall

12-06-2004 13:46:16




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 Re: Positive Ground in reply to Orion, 12-06-2004 13:43:37  
The tractor has been converted to 12 volts, the negative ground is correct.



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