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Positive ground mix-ups

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wkw

05-04-2006 09:24:18

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What happens if a positively ground diesel tractor is hooked up to the battery backwards (ie hooked up as a negative ground)? Would the tractor still run, parts get destroyed etc?

Thanks
Ken

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Island A

05-05-2006 10:39:25

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Re: Positive ground mix-ups in reply to wkw, 05-04-2006 09:24:18

When a buddy of mine switched out the battery on my JD A he hooked it up negative ground and not much happened. It still ran fine. What DID happen though is I went to jumpstart my truck thinking it was still hooked up positive ground. We had a "little" explosion.

Moral of the story, ALWAYS check for the + and - signs on a battery before jumping.

Dave

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farmermatt

05-05-2006 04:57:23

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Re: Positive ground mix-ups in reply to wkw, 05-04-2006 09:24:18

Hired help switched em up on my freightliner while installing a starter. Cost me an alternator rebuild. Also the radio, electric fuel shut off, and all the eletric guages quit until the problem was found. The guages were actually pulling backwards, pegged hard at zero.

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wkw

05-04-2006 19:20:09

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Re: Positive ground mix-ups in reply to wkw, 05-04-2006 09:24:18

Another question.

When I go to repolarize the generator am I going to have any problems properly identifying the "A" terminal on the voltage regulator? Is it easy to mix up the 2 generator terminals?

Thanks
Ken

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souNdguy

05-04-2006 20:52:59

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Re: Positive ground mix-ups in reply to wkw, 05-04-2006 19:20:09

Field wire will be smaller than armature wire.. should be easy to tell them atart.. vr should be marked anyway...

Do figure out if it is an a-circuit genny.. or a B circuit genny before you polarize it... they polarize differently.. and polarizing an A like a B can cause smoke to leave expensive parts..

Soundguy

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wkw

05-05-2006 06:47:02

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Re: Positive ground mix-ups in reply to souNdguy, 05-04-2006 20:52:59

I am really going to show how green I am at things mechanical - how do I tell the difference between an A circuit and a B circuit generator?

Again thanks to everyone for providing all this wonderful information!

Ken

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souNdguy

05-05-2006 11:34:36

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Re: Positive ground mix-ups in reply to wkw, 05-05-2006 06:47:02

Assuming it is oem.. check your manual and see what the manufacturer equipped it with.

If that fails.. and it is a unit that uses a votlage regulator.. flip the reg over.. and look for small wire wound bias resistors. On an a circuit job.. there will be a bias resistor from the field contact to ground. On a B circuit, ther will be a bias resistor from the armature contact to the field contact.. some B circuit gennies also have a 2nd bias resistor.. etc.

Soundguy

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jones in texas

05-04-2006 17:43:09

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Re: Positive ground mix-ups in reply to wkw, 05-04-2006 09:24:18

In most cases if the battery has been charged backwards it will never accept correct charge and will have to be replaced. Based on experince as battery and electrect shop owner for 16 years

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Dachshund

05-04-2006 13:44:24

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Re: Positive ground mix-ups in reply to wkw, 05-04-2006 09:24:18

It will still run, but it won't be good on your battery or your VR. Did that to mine - nephew put in a new battery and hooked it up backwards. Did't check and 3 weeks later (after having to charge it several times), it wouldn't start or charge. Got to looking and found the battery hooked up wrong. Ended up replacing said battery and voltage regulator.

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05-04-2006 12:25:17

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Re: Positive ground mix-ups in reply to wkw, 05-04-2006 09:24:18

Pete is right, we had a JD 1010 that was hooked up backwards, when we hooked it up right it would not charge. Just had to polarize (sp) the generator. After that everything worked fine.

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wkw

05-04-2006 12:07:07

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Re: Positive ground mix-ups in reply to wkw, 05-04-2006 09:24:18

What has happened is that I bought a B414 from a neighbours uncle. The neighbour put a new battery in it, as it didn't have one, and connected it as a negative ground. I didn't know it was a positive ground till I found this wonderful bulletin board.
The tractor runs but I have to charge up the battery every weekend. I have run it for about 5 hours this way so this weekend I'll reverse the battery connections and repolarise the generator and see if I have not wrecked anything.

I appreciate the input that you all have provided.

Thanks
Ken

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John T

05-04-2006 10:33:30

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Re: Positive ground mix-ups in reply to wkw, 05-04-2006 09:24:18

wkw, since its a diesel and since the starter still turns the same direction regardless of reverse polarity, I dont see any reason why it wouldnt still run unless it had some sort of electrical solenoid shut off that might be polarity sensitive, but I doubt it.

There exists a possibility you may have caused some harm to a Voltage Regulator if it has that and a regular old DC genny system versus an Alternator. If you hooked up an alternaotr system backwards it might fry the alternator. I would hook her up correct n repolarize the genny n see what happens.

John T

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Pete76NY

05-04-2006 09:52:39

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Re: Positive ground mix-ups in reply to wkw, 05-04-2006 09:24:18

It'll still run, no damage, worst case scenerio is you may have to repolarize the gen. easy to do by jumping 2 terminals on the regulator, don't remember which at the moment.

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