1940 caddilac wiring poss or neg ground ???

I am working on a 1940 caddilac limo with my dad and I have two diagrams one is poss ground and the other is neg ground for the wiring.

before hooking the guages up I would like to know what is right.

Brad

Would it be possible for you to "scan" and E mail to me a wiring diagram that you have, that says 1940 Cadillacs have a "negative" ground electrical system ? This would be most interesting, as most pre-war GM cars had a POSITIVE ground system.

Found out the hard way.....our 1940 Model 60S has a positive ground 6V system. Someone before me put a 12V battery and did it as a negative ground.

pretty sure it's positive ground....next time that I remember i'll look at my '40 la salle. my '41 cad was changed to 12v negative ground by a previous owner and not all the gauges are hooked up yet...

Pretty sure that prewar GM, Ford and Chrysler were positive ground.

Pretty sure that prewar GM, Ford and Chrysler were positive ground.

On that note, I own a 1937 Pontiac (GM) that is negative ground.

I had a 1940 Model 7219F & it had a 6 volt positive ground system.

Negative Ground

Cadillacs through 1942 were positive ground, beginning in 1946, NEGATIVE ground. Buicks were negative ground throughout the 30s and 40s--at least my 1934 was. Strange that GM did not have a standard ground...

My 1915 Buick truck is negative ground

1936 Chevrolet is negative ground--I think 1930's (at least mid-30's and later) Chevrolets were negative ground.

1940 Olds 90. Negative ground.

Take a look at the battery cable leads, and see if one end has a larger end or not, if the cables have not be changed you can tell that way, and look at the ignition coil to to see if the neg terminal goes to the distributer or the pos, , and set the battery that way, and re polarize the generator to make sure it will charge the battery in what ever setup you have,, as the car really does not care, even the radio does not care what polarity you have, unless you have a solid state viberator in it..

grimy speaks the truth,kemosabi.

and my 1930 chevy is neg grd also.

I would check the regulator points - they use two different types of metal for the points depending on the +- ground. At least you may want to polish them a little and check for stuck points.

Ron

My 1941 Cadillac is Positive Ground

my 1940 60 Special has a positive ground and the shop manual wiring diagram shows positive ground. Tom

Yep, Positive ground. Shop manual is correct.. How about that!

The Cadillacs I work on 36 39 40 41 42 are ALL positive ground.

Packard, Hudson, Chrysler, Ford, Nash, Studebaker, everyone but GM in those years was positive ground. Far as i've seen, Cadillac was the exception at GM, being the only division in those years to be positive ground.

Wonder what the thinking at GM's other negative-ground divisions was. Anyone have a sound engineering reason? Have often wondered.