which is pos vs neg

silas · Oct 9, 2009

I have made a rookie mistake! I took in an old tractor (came with the barn) that, no kidding, is probably a cwc foundry block on a homemade frame. So, I took the battery out to get a new one - but both batt cables are black. I couldn't see the terminal markings so I scratched the battery so I could clean it up and tell which is which - well I had to turn in the old batt to get the new and now I don't know which is which. All I know is one is bigger than the other. Any tips on how to figure them out? Thanks for any advice.

doogdoog · Oct 10, 2009

Aloha,
I don't know if this will apply in your situation but usually the pos terminal is larger than the negative terminal. I would try fitting the battery cables on the battery and the snuggest one should be it.

Mahalo,
doogdoog

IH2444 · Oct 10, 2009

If you have a DC voltmeter use it. When you read around the battery voltage in a positive polarity the red lead will be positive.

Anonymous-0 · Oct 10, 2009

Did you follow the leads to see where they go?

Reminds me of being out to sea and finding a good fishing spot then marking the spot by putting an X on the side of the boat.

MarkB_MI · Oct 10, 2009

99.9 percent of old tractors have six volt positive ground electrical systems.

If the tractor has been converted to 12 volts, as evidenced by an alternator instead of a generator, it will be negative ground.

If you happen to get the battery in backwards on a generator system, it's still going to run although it might not charge.

John B. · Oct 10, 2009

The positive post on the battery is the one larger in diameter. After it's in service the positive post will also take on a darker color gray look.

tractorhead · Oct 10, 2009

Bendee;make sure you have the same boat next time fishing.....

RodinNS · Oct 10, 2009

NUMBER ONE THING TO DO....
LOOK to see if it has an ALTERNATOR or a GENERATOR.
If it's got an alternator, it's negative ground. If this is the case, chase the cables up to the starter/solenoid and the hot one will be the positive...

If it's got a generator, it really won't matter which way you hook it up other than you will have to reverse the primary coil wires from one terminal to the other and repolarize the generator IF you hook it up differently than it was.
Keep in mind that if you hook an alternator up as positive ground you will fry the regulator INSTANTLY.

Rod

IH2444 · Oct 10, 2009

Yep hook it up backwards with an alternator and you will be changing or repairing the alternator.

Positive ground alternators do exist but are very rare in the USA.

RodinNS · Oct 10, 2009

Yes, they are indeed rare. I've read about them but never actually seen one...

Rod

silas · Oct 10, 2009

So anyway, I got over my brain fart and noticed the big cable was bolted to the engine block and the other went to what looks like a starter. Duh. Now my problem is what kind of fuel runs in it. The tank is dry and smells like kerosene. Could it run on kerosene? I"m guessing not - so anyone know if diesel or gas smells like kerosene when it evaporates over time? Thanks for everyone"s help so far. Here"s a photo - I"ll also upload it in the tractor photos section. Also, there"s an oil tank, too - about half full. Anyone have a recommendation on oil type? Thanks.

barn E · Oct 10, 2009

Follow the ca bles, impossible to go wrong.

which is pos vs neg

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