C15A Battery hookups

[Eric R.]

Ok this maybe a dumb question but I just need to confirm how the battery is hooked up on a C15A.

I have looked at the electrical schematic I have available but it doesn't show the polarity of the battery and the leads on my vehicle are a single color replacement (giving me no clue). So is the C15 a negative or positive ground?

Just need to make sure before I go and fry something I shouldn't!

[Bob Carriere]

I Eric

It is possible that originally they were positive ground but all I have worked on are Negative ground.....which is what I have on my C15a..... and that is how I got it but would not vouch that it is accurate.

At least my starter does not run backwards......

Bob

[Eric R.]

Thanks Bob. I had two different replies from two different people when I asked so I thought it would be best to come to the font of knowledge!

[Grant Bowker]

Like Bob's, my C15A is wired as negative ground and starts and runs. I believe commercial Chevs of the period were negative ground but commercial GMCs may have been positive ground (but at least one source gives the CCKW as negative ground). Two branches of the same company using different conventions - a good recipe for confusion.

The Maintenance manual for Ford CMPs MB-F1 shows positive ground in the wiring diagram on page R-2 (hopefully a Ford owner can confirm this). The corresponding wiring diagram in the Chevrolet Manual MB-C1, page R-6, shows a negative ground.

[Phil Waterman]

Hi Eric

Not a dumb question at all, because both Negative and Positive Grounds were in use at vehicles at that time.

Now to CMPs all three of mine are negative ground, 1941 C60L, 1942 C60S, and 1945 HUP. (If one had been different I probably would have changed it just to match the others, devil of a thing when your trying to jump vehicles in the dark.)

The MB-C2 and MB-C1 clearly shows negative ground put the only place I see this is on the actual wiring diagrams.

Cheers Phil

[rob love]

As far as I have ever seen, chev is negative and Ford is positive.

[Eric R.]

Thanks guys. I know I have worked on ford civilian trucks from the era and they have used a positive ground. My tractors from the era also use a positive ground.

I don't have the manual referenced yet. Guess I will need to get a copy from fleabay.

[Andrew Rowe]

Whether the vehicle is positive or negative, you should check what side of the coil that the wire comes goes to the dizzy. This will actually tell you which way it should have been connected up. The coil has 2 terminals , pos and neg.
I think by memory , but correct me if I am wrong ,is that neg earth on vehicle
you run from the neg side of coil to dizzy. If you do connect vehicle up wrong, sometimes the generator will need "polarizing" again so it will start charging, but that is another issue, and sometimes does not always need doing. Confused now!

[Eric R.]

Originally Posted by Andrew Rowe

Whether the vehicle is positive or negative, you should check what side of the coil that the wire comes goes to the dizzy. This will actually tell you which way it should have been connected up. The coil has 2 terminals , pos and neg.
I think by memory , but correct me if I am wrong ,is that neg earth on vehicle
you run from the neg side of coil to dizzy. If you do connect vehicle up wrong, sometimes the generator will need "polarizing" again so it will start charging, but that is another issue, and sometimes does not always need doing. Confused now!

I'll have to check that. My truck has had a 261 swapped in and the coil is mounted up above the engine instead of in the little isolator box on the cab frame. Shouldn't make a difference though but i will check it.

[cletrac (RIP)]

On any of the old 6 volt systems I've seen, Chev is negative and Ford is positive.

[Eric R.]

Oh and while were at can anyone give me an idea of what length the original battery cables were? I need to have a set made and want to replicate the original length.