from positiv to negative ground

G

gillis

Junior Member
Hi everybody, i have some questions. I bought a 1930 mod A with a rebuilt generator, they changed it from positiv to negative ground ,( It's still 6v) my question is what do i need to Think about more ?


q2 what is the area of the Cables from the generator and the starter motor? and finally is there anyone who has a wiring diagram of the conversion from pos-neg ground? and what area there is on the cables in the harness. Hope you can help me ,thanks / Gillis :):)
 
You do not have to change anything but the battery cables on the battery, ampmeter leads and re-polarize your generator.
 
Since Model A's came with 6 volts positive ground, I would keep it that way.

Always polarize the generator if it has been worked on or the battery polarity has been changed by using a short wire to jump the 2 cutout terminals for one second.
 
I am trying to keep my model A as "stock" as can be. That being said I have to leave my car in storage for quite some time each year ( hope that changes SOON) but in the mean time just something in me says that leaving the positive hooked directly up to the car while away might cause a problem - the least of which is drain the battery or worse might cause a more severe problem. That means either at least unhooking the positive lead or removing the battery. The quickest, easiest, and I hope safest was to change to negative ground and install a quick switch that disables the battery when the car is not in use. I purchased the switch and mounting bracket from Bratton's and did the change. It was quite painless and quick. I did change the ammeter leads and the coil leads. I did not do anything to the generator in regards to polarity because I was so happy everything went so easy that I completely forgot the generator routine. Maybe I was just lucky but when I started it up the generator was charging great and everything has worked fine since. I did that about 2 years ago and so far I am very happy with it. Jim
 
Jim M said:
I am trying to keep my model A as "stock" as can be. That being said I have to leave my car in storage for quite some time each year ( hope that changes SOON) but in the mean time just something in me says that leaving the positive hooked directly up to the car while away might cause a problem - the least of which is drain the battery or worse might cause a more severe problem. That means either at least unhooking the positive lead or removing the battery. The quickest, easiest, and I hope safest was to change to negative ground and install a quick switch that disables the battery when the car is not in use. I purchased the switch and mounting bracket from Bratton's and did the change. It was quite painless and quick. I did change the ammeter leads and the coil leads. I did not do anything to the generator in regards to polarity because I was so happy everything went so easy that I completely forgot the generator routine. Maybe I was just lucky but when I started it up the generator was charging great and everything has worked fine since. I did that about 2 years ago and so far I am very happy with it. Jim
Click to expand...





Why is it quickest, easiest and safer to change to negative ground and then add the switch ?
Many have just added the switch only.
 
Here's a little piece on this topic that I wrote a few years ago.​
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Why Negative Ground?​

A recent forum discussion thread on the fordbarn.com web site motivated me to go back and look again at an article in the Skinned Knuckles magazine. The article, "Why Negative Ground?" was in the September 2009 issue, #398. The simple question about a relatively modern occurrence was asked by a reader: Why did all remaining positive-ground U.S. manufacturers switch to negative-ground in 1956? After extensive research seeking an answer, the frustrated editor concludes,

"Much as I would like to announce that we have an answer, unfortunately just the opposite is true. Not only have I not obtained facts, but I am also puzzled beyond belief that the wide variety of automotive historians and curators whom I questioned could not come with a factual answer."

One U.K. electrical engineer and museum curator who was queried on the subject replied, "You have opened a can of worms..."

The SK article includes a table showing ground usage by 35 car models since 1932. Twenty five of those used positive ground for at least part of their existence. The various models that became part of GM, except for Cadillac, always used negative ground, as did Duesenberg, Essex, Stutz, and Reo. Cadillac switched from positive to negative ground after WWII. Hudson switched from negative to positive ground in 1934, and then back to negative in 1956. The "universal" switch to negative ground never occurred in the U.K. Nash Metropolitans remained positive ground, and allegedly some US car models made for export to the U.K. are still set up with positive ground.

The various creative, speculative or bogus rationales supporting one or the other grounding usage that have been offered over the years, including the corrosion thing, are briefly reviewed. The fact is that in 1956 there was a sudden consensus that it would be a good idea to standardize, but exactly how and why that consensus emerged at that moment in time remains puzzlingly mysterious.

I think it's clear that there really is no strong argument to be made one way or the other, but standardization is a good idea, and, happily, it came to pass! Too bad Ford was on the wrong side of history, but it's no big deal.

Steve Schullery
 
My guess is the switch maybe had more to do with electrical accessories --radios for example.
 
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There is an additional concern that is seldom mentioned or addressed. The battery terminal connectors. The Pos and Neg actually have different size posts. If you use the same original ground connector and starter lead you can do a hack job and make the fit to wrong post sizes by over stretching one and over clamping the other or you can preserve the original cables and replace them.
StandardDINBatteryPost.jpg

The original Ford starter lead was #2 AWG (NOT 2-0 or 00 !). On 12V #4 AWG would be plenty for a Model A, probably overkill. Many small modern cars use #6 AWG.
 
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One friend changed his stock Model A to NEGATIVE ground, as it always screwed up his BRAIN, when troubleshooting, as ALL his other cars were NEGATIVE ground.
Bill W.
 
gillis said:
Hi everybody, i have some questions. I bought a 1930 mod A with a rebuilt generator, they changed it from positiv to negative ground ,( It's still 6v) my question is what do i need to Think about more ?
Click to expand...

How does one rebuild a generator for positive ground?

Just switch the battery around, then jump the 2 cutout terminals for a half second to polarize the generator and off you go.
 
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