6 or 12V DC Reverse Polarity

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twayne

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ALCON,

I realize this is not a usual electrical question, but I'am wondering if anyone knows of a logical reason for older model equipment/vehicles using reverse polarity? I have several friends that own tractors ex. JD 12V and Ford 6V both reverse polarity that ask if would harm anything if they switched to negative ground on the JD and or install a 12V battery(negative grounded) in the Ford.

Thanks in advance,

Wayne
 
I'm not old enough to know why some of that old equipment used a positive ground system, but I've worked on enough to know that switching to negative ground is a chore. You need a new starter, cause the old one will run backwards, a new generator cause the old one will be trying to discharge your battery, and a new voltage regulator cause... well, just because. The lights, if you have any, should work just fine.

Going from 6 volts to 12 volts is pretty much the same as above, but the lights won't work for more than a few seconds. You'll have to change them as well.

On the other hand, nothing starts as easily as those old Fords, so why mess with it?
 
twayne said:
ALCON,

I realize this is not a usual electrical question, but I'am wondering if anyone knows of a logical reason for older model equipment/vehicles using reverse polarity?
Click to expand...
I can answer that. For the same reason telephone offices use positive ground systems, to prevent corrosion.
 
Reverse Polarity

Reverse Polarity

Thanks Guys,

I agree most of those old Fords do start well. Belive most of the folks that convert their old equipment to 12V is because they probably need a tune up or rebuild and an extra twist from the 12V usually gets them going. Never the less, still don't understand the use of a possitive ground. G0049, I must be too old, coming from a farming community we did things a little different, on a as needed basis. I have personally used a 12V battery with the starter (6V) that came on the equipment (Fords, Avery's, Minninappolis Moline's ect.) on many occassion for extended periods of time (years) without causing any problems. The main reason for doing something like this was the simple fact that a 12V battery was available and the 6V was not and we had to keep on keeping on (economic distress). I'm sure this practice is not politically correct but believe it or not it worked very well. This was done with nothing else being changed, no resister, same coil and same old generator, last but not least the 12V battery was installed "Negative ground". Friends and aquaintences has seen these foolish things I have tried, guess that's why they're askng the reason need for a possitive grounded system, especially when they don't use them any more on any wheeled or track equipment that I know of.

Being in the electrical/equipment arena for many years I've been asked this question many times and never could come up with a reasonable answer. dereckbc, I think your answer is the best so far, "use a positve ground to eliminate corrosion". Don't really know why but that's the answer I'll use the next time someone ask. They'll probably ask why corrosion would be less connected with positve ground and why everyone changed to negative ground. We'll address that issue another day.

Thanks again,
Wayne
 
I've used 12 volt vehicles to jump start old 6 volt equipment many times as well, usually with no problem. They start quick enough that the starter doesn't get too hot. Only time I really had a problem was an 8N that wouldn't fire (ants had colonized the distributor) and my helpful brother-in-law just kept cranking.

Wish they made new equipment as sturdy/forgiving as the old stuff.
 
You do not need to replace the starter to change to 12 volt negative ground, you only replace the starting solenoid, generator and regulator, (with a bit of modification you can upgrade to a delco alternator with built in regulator) The starter will run the same direction regardless of the polarity. You will also need to install a dropping resistor for the ignition coil, as 12 volts will eventually melt down the coil. The resistor is available at any auto parts store. The tractor will start much quicker and easier. I have a 50's model 601 Ford that I've done the conversion on, along with a 51 Case that my grandpa bought new.
 
I have read that the negative-ground system results in a spark that ignites the flame better.
 
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