Positive Ground on Tractor.

[Anonymous-0]

Is there some one who would take the time, and explain positive ground to me. I was surprise to read, my John Deere 1947 Model M is positive ground. Is there an advantage to this, or is that just how they did it way back then. I'm not the best, when it comes to electrical, on engines. Thanks for any help I may receive back. Is it so simple, that I should know all about it?? Don

 

[Anonymous-0]

Positive ground works. Negative ground works. Neither works better than the other. Radios demand the proper polarity as do alternators with rectifiers. Generators with magnetic regulators don't care so long as they are polarized before running. Ignition coils put out a better spark if they have the right polarity on the primary. Ammeters read right if connected with the right polarity.

Otherwise the equipment on the tractor doesn't care about polarity. In the era when electric systems began to be applied to cars, trucks, and tractors, there were two schools of thought, one though positive ground was better, the other thought negative ground was better. Ford vs GM essentially.

When JD diesels came along, they came up with a combination system where half the loads were positive ground and the other were negative ground while the starting and charging weren't really grounded, except at the middle of the battery. Like a diesel 3020 or 4020 as it came from the factory. Still works, but confuses some who then can't repair it.

I think the choice of polarity comes back from the choice of polarity on a trolley wire that leads to corrosion of a nearby underground water pipe. Depending on where the water pipe is with respect to the power plant, one polarity eats holes and the other doesn't. That's different if the pipe is far from or near to the power plant feeding the overhead wire where the other side of the DC circuit is made up of earth and the rails.

So some figure that positive ground means the ground connections won't corrode as much as they would have with negative ground. It depends more on the materials of the ground wire and the chassis, than on the polarity. If one corrodes less from current the connection was loose anyway and should have been cleaned and tightened.

Just be careful to not touch frames if you want to jump a positive ground tractor with a negative ground truck. Keep the polarity at the battery in mind, positive to positive and negative to negative and it will all work just fine. Cross the polarities and you get smoke, sometimes a bang from one or more abused batteries to accompany that smoke.

Gerald J.

 

[Anonymous-0]

Thanks for the info. One question. If I stayed with a negative ground, opposite of what my manual says for my tractor, would all the wiring be the same, as I run my harness to all components. This is a restoration, and I don't want to make a mistake at this point. Perhaps I should just stay with positive ground, and know that it will work, when I turn on the switch. Thanks for your feed back. I was impressed that you took the time to help me. Wow!! I wish you were my neighbor. Now, I'm a plumber. I know I could plumb water to anything. Thanks again. Don

 

[Mark Benware]

difference between pos and neg ground for a plummer...... I think that would be from the septic to the well instead of the well to the septic.......maybe a little simple but here goes my laymen terms of understanding........

DC electricity want to go on a path from the + terminal to the Negative terminal, hopefully while on this path doing some work for us, (fan, light, starter etc..).

With a negative ground system the + terminal is isolated from the tractor and a wire brings the current through to the "device" where the electricity does the work and then returns to the - terminal through the tractor, hence the reason the Negative terminal is "grounded" to the tractor.

With a Postive ground the negative terminal is isolated from the tractor and current is sent through the tractor and is isolated back to the negative terminal through wires.

Positive ground.... + Cable to the + terminal or to the tractor itself and negative to the - "negative terminal"

I hope that made it as clear as mud

I would leave it as it was produced as that would be the purest way to restore the tractor and there areno negatives to doing this. Just my thoughts.

 

[Tor]

Don,

Yes, you can use your harness. Cables don't care of which direction the current flows.

However, if you decide to swap + to - to ground your starter will turn in the wrong direction and you will (probably) need to remagnetize your generator / voltage regulator. Assuming you don't have a defroster fan ;-) which also will run in the opposite direction...



Modern turn-light flasher relays are also sensitive to polarity.

regards Tor

 

[blinwmiaol.com]

LOL, the starter will not turn backwards if you switch polarity. The starter could care less what the polarity is, it just cares that there is a flow of electrons going thru it that makes the armature turn.

 

[Tx Jim]

Bid "D"[/quote]pposite of what my manual says for my tractor

Which manual operators or tech? Either one I'd throw in trash if it was for my model tractor.

 

[Anonymous-0]

I would stay with the positive ground. Otherwise you will need to change the leads on the ammeter and reverse the terminals on the coil as well. I had an engineer who worked for a tractor manufacture tell that the goverment decided that they wanted all vehicles with negative ground. This was when alternators first became standard. Before that there were some positive ground alternators.

 

[John T]

Big D, I agree with my engineer friend Gerald J. The story Ive read is that some (Ford and Chrysler) thought there would be less corrosion when frame members attached if they used Positive ground. Later negative ground became the standard

ALLLLLLL Two Cylinder Deeres were Positive ground.

If you wanna swap (I WOULD NOTTTTTTTTTT)

Ammeter leads needs swapped or it would read bass ackwards,,,,,,,,Generator needs re polarized,,,,,,,Coil wires need swapped,,,,,Despite some mis information posted below THE STARTER STILL TURNS THE SAME DIRECTION REGARDLESS OF POLARITY

John T

 

[John T]

The starter still turns the SAME DIRECTION regardless of polarity

YES you need to re polarize the GENERATOR

NO you dont polarize the Voltage Regulator

Hope this helps, best wishes

John T

 

[JDemaris]

Postive ground systems were often chosen by followers of Paul Dirac's "Hole Theory."
He came up with the theory in 1930, and he was Great Britain's equivalent to Albert Einstein.

There are advantages to both in specific situations. Overall, they both work as well.
Postive ground is still used in many electrical systems with special uses and problems, especially in military-marine use.l

In regard to tractors using it? Tractor companies adopted automotive systems that were in use. With automotive, back in the early 1900s, there were two different schools of thought, focusing on two competing electrical theories.
The "Hole Theory" and the "Electron Theory."

Neither has ever been proven or disproven, and both are still applied to certain systems.

When semi-conductors came into common use for comsumer-lever products, a stanard ground system had to be chosen, or things would of been too confusing. It was a total crap-shoot, and negative ground was chosen. Not must different than when VHS was competing with BetaMax with video recorders and player, or the recent thing between Blue Ray DVDs and the Sony system that lost out (can't even remember what it was called).

 

[Anonymous-0]

Actually in conventional computed current flow yes the current goes from positive to negative. In reality its electrons with a negative charge that flow from negative to positive. The math and equipment works for either way of thinking. The problem comes from a guess made by Ben Franklin more than a couple centuries ago. He guessed a current flow polarity and direction and set the polarity of the chemical battery and the expected moving particles carrying the current. Except he guessed wrong and that made electrons that do the moving to have a negative charge.

There are starters with permanent magnet fields (really new stuff) that are polarity sensitive. Most older starters have a wound field and are not polarity sensitive. The only reason to polarize a generator is so that it builds up from residual magnetism with the correct polarity. You don't polarize an alternator, it always builds up the same but you can't use a modern negative ground alternator on a positive ground system, but there have been positive ground alternators (takes reversing the rectifiers and the regulator inside) and floating alternators (primarly for trucks made by Leece-Neville).

Positive ground is most likely original (and it is original in JD gas tractors). It works. Negative ground with the precautions I've typed out before works. I don't think its a big deal to change, but its nice to keep things original. Battery cables don't fit well when the battery is reversed. That's on purpose to keep down accidentally reversing the battery.

Gerald J.

 

[fixerupper]

Leaving it Positive ground is less confusing. However, there's one big safety point to consider when using jumper cables from a negative ground car/pickup/tractor to a positive ground tractor.

My dad never could figure out the battery polarity thing, and one time he tried jumping a positive ground Deere with a pickup that was negative ground. He went ground-to-ground and hot-to-hot with the jumpers. When it flashed and smoked he came and got me to finish the job. Jim

 

[Anonymous-0]

Half the cars and trucks built in 1940 were positive ground/All 6v tractors were positive ground.Mechanics in the 40s and 50s had to be aware of the differences when they worked.

 

[Anonymous-0]

Gerald you have been most helpful. Thank you for all your time and efforts. I've learned allot. I'll stay with the positive ground. Thanks to all who responded back. I never knew there was such a great family of tractor lovers and associates. I'm impressed. Big'D' (DON)

 

[Lee B]

Wikipedia says:

Changing a battery -
In modern automobiles, the grounding is provided by connecting the body of the car to the negative electrode of the battery, a system called 'negative ground'. In the past some cars had 'positive ground'. Such vehicles were found to suffer worse body corrosion and, sometimes, blocked radiators due to deposition of metal sludge.
http://en.wikipedia.org/wiki/Starter_battery

The change to negative ground started to take place a decade before semi-conductors and two decades before alternators became popular on automobiles, so neither of those reasons works for the why did they switch question. Today you can buy all the positive ground alternators you care to, all it ever took was money and a dedicated search.

They switched because even high school chemistry students understand that the electron flow into a steel body will not corrode it but the opposite flow will. I guess they just don't care about the frame corrosion or maybe because it has more iron to sacrifice, that's OK? I have no comment on radiator deposits.?!

In the early days they probably thought positive things about a system with a positive ground not realizing at the time when they built them that way, that the electrons actually came out of the battery at the negative post due to Ben Franklin's wrong polarity guess. I always heard that the negative ground vehicles started easier in very cold weather (better grounding system?), but just like the wiki article, that is pretty much unsubstantiated as well.

In a hundred years when the same subject comes up, they won't be able to even buy a clue will they?