Ground Polarity

[58_BN4]

Folks, I happened upon this forum a few weeks ago, and have spent hours reading post after post. An amazing number of “Oh, now I see!” and “What a great idea!” moments. An incredibly helpful and knowledgeable group of nice people - my Thanks.
Ric in Phoenix, AZ. My project is a 58 100-6 purchased completely dis-assembled, a bare chassis and in dozens and dozens of boxes. Like many of you I’m sure, I thought with a Moss catalog and Haynes manual “How hard can it be?” Really? I have a rather basic, but perplexing question – How does one determine car’s ground polarity? How do I know if my car is positive or negative ground. I now have a re-built engine/trans. and new wiring harness installed, and am not too far from attempting to fire it up – seems a right fine time to determine this fundamental issue.

 

[GregW]

Hi Ric,
Welcome to the Forum. Most of the car won't care how you set up the electrical system. The main issue is if the fuel pump is polarity sensitive. Is it an original pump or new? The only other thing to do would be to flash the generator coils.

 

[andrea]

Here are one good article on the argument
https://mgaguru.com/mgtech/electric/et099.htm
and one on the advantages of the Positive Earth
https://mgaguru.com/mgtech/electric/et099.htm
My option is for Negative Earth on my AH
I have decided for the Alternator MOD
Cheers
Andrea

 

[57_BN4]

Quick test is to check the size of the battery cable terminal clamps. If they are still in the original position and haven't been butchered, they should only fit on the relevant battery post as the posts are slightly different sizes.

[edit] I'd flash the generator either way

 

[58_BN4]

Thanks all, thought it was much more complicated. I have a new fuel pump in box, sure to be neg ground. Generator is partially re-built, so shall polarize. Only tachometer to review.

 

[GregW]

If you have an original tach, that should be mechanical and wouldn't care about polarity.