positive to negative ground

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Martin
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positive to negative ground

Post by Martin » Mon May 12, 2025 12:01 pm

My Model T (1916 with a 1921 starter engine) came to me wired with positive ground. I would like to change it to negative ground (just because that's the way Ford did it).
Advice please: Can I simply polarize the generator by putting B+ to the field, reverse the battery cables, and go? Will the cutout work with no change? Should I replace the cutout with a regulator?
Martin


speedytinc
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Re: positive to negative ground

Post by speedytinc » Mon May 12, 2025 12:20 pm

You are correct. A mechanical cutout doesent care.
If you have a diode/electronic or Fun projects type cut out it matters. Be sure of your cutout type.


John kuehn
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Re: positive to negative ground

Post by John kuehn » Mon May 12, 2025 1:57 pm

So do you still have to do anything to the generator by polarizing it or etc? If it has the std. mechanical cutout it doesn’t make any difference.


speedytinc
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Re: positive to negative ground

Post by speedytinc » Mon May 12, 2025 2:15 pm

John kuehn wrote:
Mon May 12, 2025 1:57 pm
So do you still have to do anything to the generator by polarizing it or etc? If it has the std. mechanical cutout it doesn’t make any difference.
Polarize The generator only. One quick spark per the manual.


Topic author
Martin
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Re: positive to negative ground

Post by Martin » Mon May 12, 2025 2:28 pm

Thanks to all who responded!


big2bird
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Re: positive to negative ground

Post by big2bird » Mon May 12, 2025 2:31 pm

Martin, with positive ground the starter works fine?


Topic author
Martin
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Joined: Tue Jan 22, 2019 8:10 pm
First Name: Martin
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Location: Northbrook Illinois

Re: positive to negative ground

Post by Martin » Mon May 12, 2025 4:20 pm

The starter will be fine. I've used 12 volts negative ground systems with several old six volt positive ground starters. But now that I think about it I'll need to reverse the wires on my ammeter.


Moxie26
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Re: positive to negative ground

Post by Moxie26 » Mon May 12, 2025 6:17 pm

Changing over to negative ground and polarizing your generator, does your ammeter show a positive charge when running without headlights on. ??


TXGOAT2
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Re: positive to negative ground

Post by TXGOAT2 » Mon May 12, 2025 6:55 pm

First of all, turn the battery cable connections around. You will also need to reverse the leads on the ammeter. I think the generator would need to be re-polarized. As far as I know, the starter doesn't need any attention.


Moxie26
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Re: positive to negative ground

Post by Moxie26 » Mon May 12, 2025 7:25 pm

Pat .... It would be physically better to remove the battery and then reinstall with the negative terminal closest to the frame rail, reconnect cables to battery, install battery, hold downs and enjoy your ride.


J1MGOLDEN
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Re: positive to negative ground

Post by J1MGOLDEN » Fri May 16, 2025 8:01 pm

I am kind of new with Model Ts, I didn't get one until 1978.

One question that has never been answered was, "why was the ground changed from negative to positive?"


Moxie26
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Re: positive to negative ground

Post by Moxie26 » Fri May 16, 2025 8:22 pm

James ... Martin started this thread referring to the car he purchased that had the battery positive grounded, a problem that comes up with the belief that Model T's were the same as Model A 's.
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Norman Kling
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Re: positive to negative ground

Post by Norman Kling » Sat May 17, 2025 10:41 pm

See my comments on your other post with this name
Norm


Moxie26
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Re: positive to negative ground

Post by Moxie26 » Sun May 18, 2025 8:07 am

Norman and all, you can check my response on the other post topic of positive and negative grounded electrical.

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