MTFCA Forum

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

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.

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.

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.

Thanks to all who responded!

Martin, with positive ground the starter works fine?

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.

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

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.

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.

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?"

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.

See my comments on your other post with this name
Norm

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