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Old 05-22-2002, 04:49 AM
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Post 39 Ford - Neg or Pos ground?

I have a wager ridin' on this one!...A loaf of homemade bread baked in a woodstove oven. Personally I wouldn't light a match in a wood stove! (i know... that was a bad one!)

My friend D has a 39' Ford business coupe w/orig flathead V8. She mentioned that it was positive ground. I thought it was odd and said that it probably wasn't stock wiring... from which the the wager developed.

I've found some alledged "stock" wiring diagrams that indicate the negative ground and to my consternation some that point to positive ground.

Which is it? !

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Old 05-23-2002, 02:07 PM
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tiger,

well, it wouldn't surprise me if it was positive-ground. My '48 dodge is positive ground, not sure when they stopped doing that.

JB
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Old 05-23-2002, 02:28 PM
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my 41 dodge was positive with original wiring.Itnow is 12 volt neg ground.
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Old 05-23-2002, 04:13 PM
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Tiger, she's right...Ford was positive ground until the early/middle fiftys. I want to say '56 or '57 went to negative ground, but I'm not sure so don't bet on that one!
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Old 05-23-2002, 05:48 PM
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Ford went to neg ground in 56 when they also went to 12volt.
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Old 05-23-2002, 06:20 PM
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Liquid Larry is right on the money on this one. I had a 55 Ford in High School 6volt pos ground. My friend had a 56Ford 12 volt neg ground. I have a 52 Plymouth now and it is 6 volt pos ground. Have also owned several tractors that were 6 volt pos ground. They are fun to jump off also when the vehicle doing the jumping is neg ground, best way is to jump straight to the starter.
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Old 11-06-2002, 02:46 AM
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How can you tell the difference by looking at it if it is a pos or neg ground system? I realize that the pos will be the gound, but if you walked up to an old vehicle like that and the battery was not in it, how would you know how too hook it up (besides the battery post sizes)
My reason for asking is a have a 1950 Lincoln and I am not sure if it is a pos or ned ground system. I got a new battery for it, and the way that the terminals look, it looks like pos goes to starter and neg goes to ground (judging by terminal size and post location on battery). However, there are new terminal wires on this car and I am not sure if the previous owner knew which way (or if he even paid attention to how he took them off).
Never had or worked on a pos ground system before so I would appreciate any info anyone could offer.

Thanks!

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Old 11-06-2002, 05:54 AM
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Not sure if there is a way to tell by looking, I always refer to my old manuels. Lincoln was strange, up until 42 they had the Lincoln negative ground and the Zephyr positive ground. In 42 they both went to positive ground, so your 50 is positive ground.
If anyone wants to know others, let me know.
Jack
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Old 11-06-2002, 06:01 AM
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Just add a note proving you can't use one car manuf. to determine if another is pos or neg. Cadillac was positive ground until 46 while all other GM was neg. Always wondered why??
Jack
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Old 11-06-2002, 04:06 PM
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Thanks, Woods. If you did hook a pos grnd system up backwards, would it immediately short to ground and blow up the batt?
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Old 11-06-2002, 05:22 PM
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Never saw one blow up but its possible. Have seen the insulation on the bat cable burned off. Have also seen a bat charged backward, had very low cranking amps tho.
Jack
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Old 11-06-2002, 08:32 PM
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So if you hook it up backwards, will you know right away? From what you said, and from what I see in a manual I have here, it should be a Pos Grnd. But the guy had the old bat hooked up backwards. <img src="graemlins/crash.gif" border="0" alt="[crash]" />
I charged that battery up, it held 6 volts. Hooked it up the same way he ad it (This was a few weeks ago) and tried to just turn it over (without the ignition on) and I couldn't get it to turn over. I kept hearing the solenoid. clicking, but no turn. The lights worked. kept trying but starter would not turn.
Cleaned all contacts.. still nothing just clicking from solenoid. Eventually, the battery only had 5 volts, and the lights would no longer work. While it was still holding 6 V, I hooked up a volt meter and clicked the starter, and it was drawing it down to 1V.
I then went and bought a Vintage DieHard battery with more cranking amps than the crappy AutoZone one that was in it. Hooked it up, lights worked, starter turned over immediately. I still didn't turn on the ignition though. So if this is a Pos ground, and I had it hooked up backwards, was I only turning the starter over backwards? Should I go ahead and try to hook the battery up like a positive ground?
<img src="confused.gif" border="0">
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Old 11-07-2002, 02:58 PM
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Lights, horn, and others would work either way. Don't know whats going on with starter!! I do know that if it is a stock Lincoln it is positive ground. I would hook it up positive ground and try it. Hope this helps.
Jack
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Old 11-11-2002, 06:10 PM
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If I rember right when I hooked up the battery wrong in my 41 ford many years ago everything worked OK except the charging system. I then had to "polarize" the generator when I hooked it up right. Phil
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Old 11-12-2002, 05:48 AM
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I seem to remember that batteries and their repective cableing in the car have different size terminal connections. If the car has no battery perhaps one could determine which cable is 'small' connector and which has 'Larger' connector. Hence positive or negative grounds are automatically established.
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