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Old 09-15-2012, 08:32 PM   #1
verrece
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Default positive ground

Two questions
Does anybody knows why Ford was chosen the positive battery grounded?
and why they switched to negative grounded after?
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Old 09-15-2012, 08:52 PM   #2
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Default Re: positive ground

Chrysler did it too. I have always heard the engineers thought it would curb rusting of the bodies because of the flow of electrons. I remember in high school in the mid-50's the theory was electrons flowed in one direction but was reversed later. Too old and too long ago to remember which was which.
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Old 09-15-2012, 09:18 PM   #3
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Default Re: positive ground

My recollection is that GM started the negative ground thing because of corrosion or what ever and everybody else jumped on board when they all went to 12V. (I think that Packard stayed positive ground with the 12V changeover.)

Also, it was originally thought that elecTRICITY "flowed" from the positive post to the negative post. It was when Edison (or someone) put a plate in one of those new fangled light bulbs and tried putting a charge on it, they found out that elecTRONS would only flow in the opposite direction from what they had always assumed it should be. So, it turns out that ELECTRICITY flows in one direction, by definition, while the ELECTRONS are actually flowing the other way. The original thinkers had a 50-50 chance with the current flow way back when, and it turned out that they blew it. All of this, of course, is IMHO!
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Old 09-15-2012, 11:27 PM   #4
Dick Webber
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Default Re: positive ground

Actually Ford started with negative ground on the Model T, then switched to positive with the Model A until 12 volt days brought negative ground back. And I still don't know why either change was made.
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Old 09-15-2012, 11:31 PM   #5
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Default Re: positive ground

So... not having any electrical training or experience what-so-ever, can I just then switch my positive and negative battery cables around and then have a working negative ground system? Why or why not?
Thank you.
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Old 09-16-2012, 02:28 AM   #6
BILL WZOREK
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Default Re: positive ground

There is more to it then just that.All your guages are set up for pos. ground. they would need changing also. I am sure there is more that others may pipe in here.
And besides there is nothing wrong with Pos. ground.
Just think of how old your car is and it made it this long. JMO

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Old 09-16-2012, 06:16 AM   #7
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Default Re: positive ground

It was Thomas Edisons great idea. Which I don't understand why, but he was a great thinker and I'm not.
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Old 09-16-2012, 10:35 AM   #8
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Default Re: positive ground

Changed my '47 over to neg. ground a few years ago when I dropped in an 8BA engine. Had to turn wires around on ammeter. Also put an alternator on with engine switch. I think that was all I did. Switched battery of course.
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Old 09-16-2012, 06:09 PM   #9
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Default Re: positive ground

If it aain't broke, why fix it????????????
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Old 09-16-2012, 06:28 PM   #10
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Default Re: positive ground

Electrons naturally flow better from the negative side of a battery in DC circuits. The 6-volt systems were designed to use the maximum advantage in electron flow & current flow for what they were designing and manufacturing at the time. Best way to put it is that the 6-volt systems were just good enough for a basic automotive sytem and the price of components were in a range that produced maximum profit. When auto manufacturers competition ramped up after WWII, it was just a matter of time before it was necessary to have higher volt/amp systems in order to function the ever increasing amount of electrical accessories that folks were wanting in their new cars. 12-volt systems provided enough power for any contengency so that's the way it went. It also provided for use of smaller gauge wire and circuit protection required less amp rating that the old 6-volt . With the higher voltage, possitive earth was a non-issue where resistance in the wiring was not going to have any significant effect until it gets corroded with time & use in rough conditions.

Aviation went to 24-volt systems to save on weight & wire length/resistance factors where circuits went all the way from the nose to the tail and wing tip to tip. Most aircraft were large and had large engines that required large starter/generator sets. so 24-volt was a shoe in there. They were mostly all negative earth systems back even before WWII.

The old original radio sets were polarity sensitive with the vibrator PDC power function that was being used at the time. You can modify the old radio sets with solid state vibrator/PDC devices that are not polarity sensitive if you want to run a negative ground system. The generator would require repolarization in order to operate. Basically it would repolarize the north & south poles of residual magnetic gauss in the field pole shoes so the thing would close the cut out relay when it starts to turn. Otherwise, a generator doesn't care what polarity it's hooked to.

Last edited by rotorwrench; 09-16-2012 at 06:41 PM.
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Old 09-17-2012, 12:48 PM   #11
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Default Re: positive ground

Remember that when the choice was made, there werent accessories like radios that were commonly available. The choice was arbitrary and Ford had the production volume to choose either positive or negative. After WW2, aftermarket stuff became available and GM had more volume than Ford. Naturally, the aftermarket goes after volume first so they developed negative ground accessories like reverbs, radios, record players, etc.
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Old 10-23-2019, 12:59 PM   #12
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Default Re: positive ground

Tom I have a 41ford business coupe and would like to put an ac unit in. I was told by speedway to install a runts device on all electric type gauges except amp meter. Will the wires that connect to the gauges become the hot wire and sensor wire ,since the original + ground supplied the juice ? Do I need to change out the wiring on the entire car ,or just add harness for the ac and other devices that will be 12v once it is converted?
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Old 10-23-2019, 01:05 PM   #13
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Default Re: positive ground

I almost forgot my flathead now has 200 hp instead of 85-95 ,as the original plan from Henry. I’m not sure if a 6v system would be able to turn over the extra compression especially on a cold day. And no ac ,and in Louisiana ac is a must
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Old 10-23-2019, 01:40 PM   #14
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Default Re: positive ground

Quote:
Originally Posted by Hemiman392 View Post
Tom I have a 41ford business coupe and would like to put an ac unit in. I was told by speedway to install a runts device on all electric type gauges except amp meter. Will the wires that connect to the gauges become the hot wire and sensor wire ,since the original + ground supplied the juice ? Do I need to change out the wiring on the entire car ,or just add harness for the ac and other devices that will be 12v once it is converted?
All you need for the gauges is the Runtz Voltage reducer. Reverse the wire that runs through your ammeter. You'll wire up the a/c unit independently from the factory wiring harness.
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Old 10-23-2019, 02:20 PM   #15
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Default Re: positive ground

Check out www.oldairproducts.com I got sweet unit for my 52 F1 many years ago. They have answers to your questions. Chap
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Old 10-23-2019, 02:26 PM   #16
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Default Re: positive ground

Quote:
Originally Posted by PeteVS View Post

it was originally thought that elecTRICITY "flowed" from the positive post to the negative post. It was when Edison (or someone) put a plate in one of those new fangled light bulbs and tried putting a charge on it, they found out that elecTRONS would only flow in the opposite direction from what they had always assumed it should be. So, it turns out that ELECTRICITY flows in one direction, by definition, while the ELECTRONS are actually flowing the other way. The original thinkers had a 50-50 chance with the current flow way back when, and it turned out that they blew it. All of this, of course, is IMHO!
You are right.

On old cars with NO solid state devices, either polarity will work fine as long as the gauge, coil etc etc are wired properly.
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