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08-01-2018, 02:35 AM | #1 |
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6v Battery negative ground
Just took delivery of a 46 Merury Coupe still on 6v. According to wiring diagram the positve is to earth.
However had a starting problem and hooked up a jump starter as per positive to earth and almost a melt dowm. This car is negative to earth? Could this have been an error wehn perhap fitting the battery? What is the effect of negative to earth.Generator appears to be chrging battery. Is it just to refit the battery with positive to earth and negative to start solenoid and all should be ok? Thanks, Phil NZ |
08-01-2018, 03:19 AM | #2 |
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Re: 6v Battery negative ground
You can hook up the battery either way and polarize the generator to charge it.
If you have an amp meter in the car it should read the wrong way with negative ground...so while charging it should read disharge. |
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08-01-2018, 03:41 AM | #3 | |
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Re: 6v Battery negative ground
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Hooked up this way with negative ground the amp meter is registering a positve charge. So to just leave it this way? or if change to re-polarise generator? Phil NZ |
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08-01-2018, 05:55 AM | #4 |
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Re: 6v Battery negative ground
Phil, By all means you can leave it that way, BUT, all your other cars are probably 6 volt pos earth. Sooner or later, you'll get caught out with this one....easier in the long run to keep all your Fords wired as they should be [pos earth].
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08-01-2018, 06:55 AM | #5 |
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Re: 6v Battery negative ground
If it is showing charge now...switching to pos earth means you have to change the direction the wire through the amp meter is going...usually just taking the ring connector off bending it to U-shape so it can be pulled out through the loop on the amp meter and sticking it back in from the opposite side of the loop.
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08-01-2018, 07:04 AM | #6 |
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Re: 6v Battery negative ground
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08-01-2018, 08:38 AM | #7 |
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Re: 6v Battery negative ground
Sounds like someone has switched it over to negative ground. You can switch it back, but not sure it would be worth the effort, if it is working ok now I would leave it. If it has a "can" coil check and see how it is wired. Negative ground should have the (-) or Dist post connected to the distributor. If not that needs to be corrected.
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08-01-2018, 03:13 PM | #8 | |
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Re: 6v Battery negative ground
Quote:
Thanks for that info. Will check that coil and i correct will leave as is and put a reminder sticker label at battery. As a reminder. Phil NZ |
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08-01-2018, 04:20 PM | #9 |
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Re: 6v Battery negative ground
They used positive to earth for max electron flow in the direction it flows best. Henry changed over in the model T days to pos earth. The difference isn't a lot but 6-volt batteries need all the help they can get sometimes.
Most stuff in the old cars isn't all that polarity sensitive that it can't be changed. On later cars with solid state electronics, polarity can NOT be changed. It would fry some electronics. The old 6-volt radios will work either way as long as it still has an old vibrator for voltage step up. If it gets changed to a later solid state vibrator then reverse polarity will kill it. |
08-01-2018, 09:45 PM | #10 | |
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Re: 6v Battery negative ground
Quote:
Checked at the coil and -ve is connected to distributor. Removed all cables from battery to solenoid to starter motor. Cleaned up, Cleaned off paint at firewall where earth secures. It now spins over good on the fully charged 6v system with the -ve to earth so will leave it in this way.. Phil NZ |
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08-01-2018, 11:11 PM | #11 |
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Re: 6v Battery negative ground
Not sure what -ve is, but if the coil is connected reverse polarity it will only function at about 80%.
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08-02-2018, 12:23 AM | #12 |
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Re: 6v Battery negative ground
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08-02-2018, 07:39 AM | #13 |
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Re: 6v Battery negative ground
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08-03-2018, 07:17 AM | #14 | |
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Re: 6v Battery negative ground
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08-03-2018, 10:27 AM | #15 |
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Re: 6v Battery negative ground
Flow of electrons are the same...it´s about what becomes the sacrificial part in the system.
In positive earth you loose a few grams of iron from the body...in negative earth it eats up your copper connectors bolted to the ground. In the battle between Ford(positive earth) and GM(negative earth) it might have been so that the big dragon won... |
08-03-2018, 04:22 PM | #16 |
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Re: 6v Battery negative ground
Flow is always from negative to positive. The flow through a conductor wire is predictable and can be manipulated by keeping it close the power source and sizing the wire for the least resistance. The ground path is less predictable about its resistance to the flow and the pathway is not as easy to manipulate.
Electric starters are what made the change with Ford. The flow is better from a source (the battery negative post) to the starter via a known resistance conductor cable with a know length of run. The bottom line is that the starter worked better with the positive ground arrangement than it did with a switched polarity. The rest of the system could care less. When 12-volt came along, resistance of the conductor cable wasn't so much of a factor with twice the voltage to kick it through. When alternators came along, the diode life is a bit more reliable with negative ground so that sort of sealed the deal. |
03-04-2020, 08:23 AM | #17 | |
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Re: 6v Battery negative ground
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03-04-2020, 12:04 PM | #18 |
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Re: 6v Battery negative ground
I agree. Good, clear explanation. Rotorwrench, sounds like you have a background as a teacher/instructor.
Now that we've gotten into the weeds of electron flow, this student has a follow-up question: wouldn't the unpredictable resistance in the ground part of the circuit have the same effect on current flow thru the circuit, before or after the starter? Last edited by JayChicago; 03-04-2020 at 12:31 PM. Reason: remove a typo |
03-04-2020, 12:57 PM | #19 |
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Re: 6v Battery negative ground
Positive or negative has nothing to do with how easy current flows...it´s a closed loop that goes from battery and back to it again...sum of all resistance on feed or ground side ads up.
If it would be more efficient todays cars in the hunt for that last % of economy would be pos ground....think of all motors not only starters used in a modern car. |
07-29-2021, 12:09 PM | #20 |
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Re: 6v Battery negative ground
I appreciate the clear explanation
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07-29-2021, 12:10 PM | #21 |
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Re: 6v Battery negative ground
Posting to reach 10 posts as required
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07-29-2021, 12:11 PM | #22 |
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Re: 6v Battery negative ground
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07-29-2021, 12:12 PM | #23 |
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Re: 6v Battery negative ground
Just trying to post the required 10
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07-29-2021, 12:12 PM | #24 |
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Re: 6v Battery negative ground
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07-29-2021, 10:38 PM | #25 |
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Re: 6v Battery negative ground
Strangely enough, the correct or proper Ignition Coil polarity has nothing to do whatsoever with whether the car itself is positive or negative ground.
It is true that hooking the coil up "wrong" will result in a less than optimal spark. Some coils marked "+ and -" and some coils are marked "BAT and GND" but either way there's a question - is the coil itself one manufactured when positive ground was de rigeur, or, is it a post 1956 coil that presumably is marked different? Fortunately there is an easy way to determine if an ignition coil is connected correctly regardless of the markings on the coil, or the vehicle polarity. I suggest using the analog style voltmeter. It only takes a second, and there's less risk of zapping yerself. See: https://mgaguru.com/mgtech/ignition/ig104.htm Why then do we worry about coil polarity? Because the spark plugs do care which way the electrons are flowing in the high tension circuit. The spark plug has a thermally insulated center electrode (surrounded by ceramic). With engine running the center electrode runs substantially hotter than the exposed end electrode. Design of the ceramic insulator determines how hot the center electrode will run, leading to the designation of hotter or colder spark plugs. As electrons go, they love to jump away from a hot surface and fly toward a colder surface, so it is easier to drive them from hot to cold rather than from cold to hot. End result is a difference of 15 to 30 percent in voltage required to make spark "initially" jump the gap on the plug depending on which way it is going. So the spark plug prefers to see a voltage potential that is negative on the center electrode and positive on the end electrode for the very first hop of the spark. Oddly enough, this has nothing to do with polarity of the vehicle electrical system, but it is influenced by the common connection inside the ignition coil. |
07-30-2021, 06:21 AM | #26 |
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Re: 6v Battery negative ground
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07-30-2021, 09:27 AM | #27 |
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Re: 6v Battery negative ground
Speaking of electric motors Flatheadmurre, When my brother accidentally hooked up my 36 dodge pickup battery to negative earth the blower fan made very bad noises. It walked the brushes out of their cradles and did not blow , it was spinning backwards. If it hadn't been for that I wouldn't have ever known what he had done as the amp gauge was not functional. We re polarized the system and all was good again. No harm done just a good learning experience.
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