TR2/3/3A Positive or negative ground?

[miamibeachbums]

Hi all, new to the Forum. 1959 TR3A, just bought it and Battery came hooked up as negative ground. But not sure if that is correct. What part of the electrical system defines a positive or negative ground for the system? Starter, alternator, etc.? Can the whole wiring system be positive or negative ground just by changing one piece of the puzzle? Thanks Danny

 

[TR3driver]

Original configuration was positive ground.

However, none of the original components care very much, the car will actually work (more or less) if you just swap the battery leads. (Sometimes they get swapped by accident.) Normally, it's best to also swap the leads at the coil (plugs fire easier with a negative spark) and ammeter (it will read backwards otherwise). The original generator can be "polarized" to operate either way. The battery posts are slightly different sizes, but usually the clamps will accommodate either post.

If someone has added an outlet for charging a cell phone, or an electric radiator fan, it will need attention too.

Of course, if you have an alternator, or anything else with electronics in it (LED bulbs, stereo, etc), you'll probably want to stick with negative ground. I knew I would probably want to convert to an alternator in the future, so I put my TR3 together as negative ground. (Positive ground alternators do exist, but are very hard to find and may not fit very well.)

PS, welcome to the asylum!

 

[Geo Hahn]

Welcome and congratulations on your acquisition. Pictures are welcome if you feel like sharing them.

Randall covered it well (of course) -- at least, since you mention an alternator, it sounds like the switch was intentional. My TR4 arrived negative ground just because the seller installed a new battery but fit it backwards. Ran okay, didn't fry the radio and all I had to do was swap it back to be positive ground again.

 

[mrv8q]

Glad to read you found BCF, a great resource for both the new and experienced TR3 owner.

 

[miamibeachbums]

Thanks Randall and all for the info. Very helpful. I will get some pictures posted as soon as I get my act together. Thanks for the warm welcome. Cheers Danny

 

[Marvin Gruber]

One thing to check, its not 100% accurate but the battery connections are sized. Pos size post is bigger. You should be able to "fit" the posts if the cables have been on the car for a while. That will give you an idea of wheather car was pos or neg grounded.
Marv

 

[miamibeachbums]

Thanks Marv. Unfortunately they changed the cables so they're bothe the same size. I figured it out. Negative ground on this one. Thanks all.