positive /negative ground?
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Forum Name: Farm Equipment
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=140385
Printed Date: 14 Aug 2025 at 11:38pm
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Topic: positive /negative ground?
Posted By: grinder220
Subject: positive /negative ground?
Date Posted: 13 Jul 2017 at 7:28pm
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Bought a D17 last week that has been sitting in a shed for 20 years or better. It didn't have a battery in it. How can tell if the ground has been reversed? Going by the ground cable post size it has a negative ground.
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Replies:
Posted By: tomNE
Date Posted: 13 Jul 2017 at 7:49pm
it'll be a good bet, if it has a generator that is a positive ground.
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AC from the start of my families farming career till the end!
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Posted By: DougS
Date Posted: 13 Jul 2017 at 7:51pm
The better battery cables I'm familiar with wouldn't allow the positive connector to fit on the negative post. Cheaper cables have the connectors sized alike. In any case it probably won't matter how you install the battery, polarity wise. At least it shouldn't hurt anything, providing the tractor doesn't have an alternator.
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Posted By: Brian Jasper co. Ia
Date Posted: 13 Jul 2017 at 8:44pm
Look at how the coil is connected. + connected to ign switch = neg ground. Neg connected to ign switch = pos ground. Originally all of A-C's generators were positive ground.
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"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford
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Posted By: Brian Jasper co. Ia
Date Posted: 13 Jul 2017 at 8:45pm
One more thing, polarize the generator before you do start it...
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"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford
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Posted By: grinder220
Date Posted: 13 Jul 2017 at 9:16pm
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Thanks for the information.
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Posted By: Gerald J.
Date Posted: 14 Jul 2017 at 10:15am
Another check a bit harder to do is the ammeter polarity. With negative ground the negative terminal of the ammeter goes to the battery, and positive terminal to the charger and loads. With a battery connected turn on the lights, ammeter must show discharge current if connected to match the battery polarity.
Flashing the generator after sitting a long time and with the battery polarity in question is important. Just sitting a long time can loose the residual magnetism in the field poles that sets the polarity that the generator build's voltage.
Gerald J.
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