How to tell if a tractor is positive or negative ground?

Brad in WI · Jul 10, 2013

I am working on a 240 Utility for a friend of mine and we are unsure of it has a positive or negative ground electrical system. My neighbor took out the battery and did not look to see what side of the battery went to the starter. Is there some wires that I can check to make sure that when I put in the battery that I have it correct. It is a 6 volt system with a working generator. We are going to replace to wrecked battery with an 8 volt and replace the one screwed up cable. I just don't want to wreck more than what was already done. Thank you. Brad

J. Everett · Jul 10, 2013

Take a look at the battery cable hooked to the starter motor, verses the ground cable, the cable that was hooked to positive will be a little larger, (big post / small post) big post on all batteries is positive.
J. Everett

504-1 · Jul 10, 2013

6 Volt is going to be Pos ground. You can check the wire from the distributor to the coil. The distributor is the ground, so the wire from the coil comes from the + post to the distributor, is is a POS ground. Do not buy battery cables at your auto parts store, the 12v cables will not carry a 6v system.(I buy short pieces of welding cable and crimp ends from the welding store)#2-OO works fine

gene bender · Jul 10, 2013

You dont need to go to 8v just get new 1ga cables and get the starter serviced. New brushes maybe a bearing and a bushing and it will go forever. You can get new 1ga cables at your local parts place NAPA ect.

Tom Fleming · Jul 11, 2013

I agree 100% with Gene. A correctly setup and clean 6V system and battery will give years of service........good service. Make it clean and keep it clean.......just like the fuel cap says.

mkirsch · Jul 11, 2013

Here's how to test:

Hook up the battery one way or the other. Turn on the lights and/or ignition switch. If the ammeter needle moves to the RIGHT, you have it hooked up "wrong."

Even if you have it hooked up wrong you can't hurt anything. There are no polarity-dependent electronics on the tractor.

Apologize in advance, because the following does not answer your question EXACTLY as asked, but you need to hear this:

I agree with others. No need for 8V. You are just going to cause more problems than you think you're solving.

There's no safe way to fully charge an 8V battery with a battery charger.

You wouldn't need an 8V battery if you had decent battery cables and the generator was working. It's only a C123 engine. If the generator is working your starter is shot.

Either fix the 6V system or convert to 12V. 8V is a waste of time.

Brad in WI · Jul 11, 2013

everything worked very well except for my neighbor when removing the battery galled up a top post cable clamp that is too far gone to repair and pryed it off and broke the post from the plates on the inside of the battery. He did not know a battery could be hooked up either way and did not pay attention when he took it out. It was removed because it only had 6.2V in the battery and he thought it was bad. He then tried to trickle charge it for a few hours on a 12V charger. He only took it out because the tractor would not start. Turns out that he had the tractor flooded and thought it was the battery cause it turned over slowly. Brad

mkirsch · Jul 11, 2013

Ouch. Sounds mechanically challenged. Does he have the willingness and capacity to learn, at least?

The worst are the mechanically challenged who either can't learn for whatever reason, or refuse to learn because they think they know it all already.

Brad in WI · Jul 11, 2013

He is an older fellow who is willing to do anything sometimes without a full knowledge of how things work. He is in his late 70's and very active but not extremely mechanically inclined. If my farmer buddy or I tell him to do something specifically he has no problem at all doing it. He was not aware that tractor was a 6V system and just assumed the battery was dead so he was gonna help us out. He meant well but also cost us a few hours of time to run for parts and repair plus the cost of the parts. Oh well, It is still nice to have him around helping us when we need the extra hand. Brad

DeltaRed · Jul 11, 2013

Brad,these guys are 100% correct!Forget the
8v.Service the starter,get new cables.Do the simple
ammeter test to determine polarity.

pete 23 · Jul 11, 2013

Most likely positive ground. If lights work it is easy to tell. You indicated it is 6 volt system so I will assume still generator not alternator or all bets are off. You can hook a couple of small jumper wires to battery, starter and ground. Turn lights on and if hooked correct the ammeter will show discharge. If hooked wrong it will show charge which of course it is not charging as it is not running. Even hooking it backwards will not cause any harm if you do not start it. If it has alternator, then I would hook a test light between batt post and ground. If it lights it is hooked wrong unless you have something turned on like lights or ign.

David G · Jul 11, 2013

I would keep it 6V, or upgrade to 12V.

willie in mn · Jul 11, 2013

Quick & dirty, takes 10 seconds, no tools, can do it in the dark.
Hook up ONE cable.
If it slides on snugly it is right.
If it slides on with lots of sloppy space,it is wrong, pos (large) cable on neg (small) post.
If it won't go on at all, it is wrong, neg (small) cable on pos (large) post.
Willie

How to tell if a tractor is positive or negative ground?

Brad in WI

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J. Everett

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504-1

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gene bender

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Tom Fleming

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mkirsch

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Brad in WI

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mkirsch

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Brad in WI

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DeltaRed

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pete 23

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David G

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willie in mn

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