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Farmall & IHC Tractors Discussion Forum
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49 H, negative ground?

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EH in KS

12-08-2007 09:53:02




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I have a 49 H. It is 6 volt. The battery is hooked up as negative ground and I know they were originally Positive ground. Can i just switch the battery back to positive ground, or do I need to change wires at the distributor, voltage reg. etc?




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Steven f/AZ

12-08-2007 13:03:35




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 Re: 49 H, negative ground? in reply to EH in KS, 12-08-2007 09:53:02  
Ya'll need to read John T's post carefully. He knows his stuff. third party image



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mkirsch

12-08-2007 12:11:35




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 Re: 49 H, negative ground? in reply to migraine, 12-08-2007 09:53:02  
The starter doesn't have any magnets in it. It's "shunt wound" meaning that both the field and the armature are electromagnets.
The way it's wired, if you reverse polarity, you reverse it both in the field and the armature. End result is the starter turns the same way no matter what you do.



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glennster

12-08-2007 16:38:17




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 Re: 49 H, negative ground? in reply to EH in KS, 12-08-2007 09:53:02  
like the others said, if its working and charging, why change it. i have a w-9 that was converted many years ago to 12v. and its positive ground, runs good, charges fine. i left it that way.



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old

12-08-2007 12:47:02




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 Re: 49 H, negative ground? in reply to EH in KS, 12-08-2007 09:53:02  
Some of the people say you need to also switch the coil wires around, BUT I have found most of the time they are still wired for + ground and if so you don't need to change that. If the + side of the coil goes to the distubutor then its set up for + ground an how



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CNKS

12-08-2007 11:49:51




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 Re: 49 H, negative ground? in reply to EH in KS, 12-08-2007 09:53:02  
The wires at the distributer need to be reversed if you go to positive ground. If it is currently charging ok, the only potential problem you may have with negative ground is that if your current voltage regulator is designed for positive ground (you will have to remove it and see if it is marked), the contacts will wear faster. Otherwise you can change it to + or leave it as is.



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Andy Motteberg

12-08-2007 11:32:50




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 Re: 49 H, negative ground? in reply to EH in KS, 12-08-2007 09:53:02  
Does it have a magneto or a distributor? If it has a distributor, you need to change the wiring if you are changing it to + ground again.



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Andy Martin

12-08-2007 10:40:32




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 Re: 49 H, negative ground? in reply to EH in KS, 12-08-2007 09:53:02  
You would need to polarize the generator is all.

If it charges now, it is OK to leave it as is.



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L.C.Gray

12-08-2007 11:16:13




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 Re: 49 H, negative ground? in reply to Andy Martin, 12-08-2007 10:40:32  
I dunwanna seem dumb asking but, I get the re-polarizing bit ok, but if the polarity is swapped at the battery connections, wouldn't it make the starter turn bassackwards?

I'm not trying to be a pain, I'm nearing start up on my first old one with a 6-volt and an actual electric starter and will have to sort out the whole 6-volt/pos/neg deal on it. I don't imagine the points and coil care about polarity at all, but I'd think the starter would reverse itself.

I guess I've just been spoiled by hand cranks and magnetos all these years

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John T

12-08-2007 12:31:16




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 Re: 49 H, negative ground? in reply to L.C.Gray, 12-08-2007 11:16:13  
1) Since the starter is a series wound DC motor that uses an elecromagentic field versus a permanent magnetic field IT STILL TURNS THE SAME DIRECTION REGARDLESS since youre not swapping the field or armature windings with relation to each other. A permanent magnet motor would reverse cuz you change the current direction in ONLY ONE of the field or armature i.e. the armature since the magnetic North/South polarity of the permanent magnet field remains unchanged

2) If its a battery powered coil igntion it still fires even at reverse poalrity but its not near as efficeint and wont deliver as much spark gap energy across the plug gap as if its wired correct i.e. swap leads if you reverse polarity

3) If it has an ammeter its leads need reversed if you swap polarity otherwise it reads bass ackwards.

4) The genny can still charge fine regardless of polarity BUTTTTT TT it needs repolarized

5) Many Voltage Regulators will work at EITHER polarity while others may not. Thinks like polarity sensitive suppressor diodes and the coatings on relay contatcs can make a difference. If its not labeled Id go ahed n try it cuz it may work fine a long time but if it quits you need a new correct polarity one anyway.

6) Points or condensor dont care nor light bulbs

7) SOME gauges are polarity sensitive IF THEY USE GALVO NEEDLE ACTIONS while the bimetallic heat type dotn care which direction the current flows

Any other polarity questions??

yall take care n God Bless

John T

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RustyFarmall

12-08-2007 11:27:31




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 Re: 49 H, negative ground? in reply to L.C.Gray, 12-08-2007 11:16:13  
The starter will not know the differance. It will spin in the same direction whether it is connected to the battery positive post, or the battery negative post. The starter doesn't care.



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