Positive or Negative Ground-What Difference?

D

Doug

Senior Member
What happens that should, and what happens that should not, when a 6 volt
battery is installed, grounding the Positive terminal in a Negative ground
system OR visa versa? (Pre1960s systems-6 volt, generator, voltage regulator, etc.)

Also, correct grounding for:
1950 Mercury V8
1953 Ford V8
 
Common knowledge just says reverse the wire through the ammeter loop on the dash. Seems too little to me. I have done just that on about 5 or 6 trucks and it was fine.
 
The effect of changing polarity depends on what is hooked into the electrical system. With old Fords, all of the instruments except the Ammeter operate on resistance elements that do not care which way the current is flowing.

No radio will work on reverse polarity from it's design. If you have galvanometer type meter movements that work off of magnetic fields from current flow, such as a voltmeter, they will work backwards and may burn out. The regulator also depends on correct polarity.

Why do you ask? What are you trying to accomplish?
 
Problems are the generator (which just needs to be polarized to work) and the coil. Running a coil with the polarity reversed drops the output down, something like 20 to 30 % I believe. And the items drolston listed.
 
JSeery said:
Problems are the generator (which just needs to be polarized to work) and the coil. Running a coil with the polarity reversed drops the output down, something like 20 to 30 % I believe. And the items drolston listed.
Click to expand...

But does revering the coil wires alleviate this problem? I have always heard the pole chosen for ground goes to the distributor.
 
GB SISSON said:
But does revering the coil wires alleviate this problem? I have always heard the pole chosen for ground goes to the distributor.
Click to expand...

That's true if you have a can type coil. There is all kinds of debate on damage to the coil running it reverse polarity, no idea on that one. But, if it works, I guess it works.
 
Supposedly when a coil has run a long time and polarity is swapped the iron core is adversely affected, the coil will work but the spark output won't ever be quite what it should be. I think Jim Linder (Bubba's Ignition Service) mentioned this.

Here's a link that discusses this polarity thing (although having nothing to do with the vehicle polarity!) it was found that a better spark occurs when the plug electrode is positive, as electrons like to jump from hot to cold. A coil will work when connected "backwards" but it will work best when connected correctly.

http://mgaguru.com/mgtech/ignition/ig104.htm
 

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Doug said:
What happens that should, and what happens that should not, when a 6 volt
battery is installed, grounding the Positive terminal in a Negative ground
system OR visa versa? (Pre1960s systems-6 volt, generator, voltage regulator, etc.)

Also, correct grounding for:
1950 Mercury V8
1953 Ford V8
Click to expand...

1950 Merc and 1953 Ford have Positive Ground

If you connect battery backwards for a short time, no damage will occur to pre-'60 cars.

Myths - iron core of coils can be adversely affected with polarity reversal - FALSE - transformer cores assume a tiny residual magnetism but doesn't affect coil performance and is quickly reversed with polarity. Most coils will produce spark either way but they are wired to produce a greater voltage only one polarity

Radios will not work - FALSE most will not work, a few actually will. ******** radios will not be harmed with reversing polarity. Some replacement solid state vibrators will likely be damaged unless the fuse blows first.

Generic voltmeters (d'Arsenval) can be burnt out. FALSE the needle will likely be bent but the coils will take the same voltage either way without damage.

I have worked professionally in above fields and hate to see these myths perpetuated.
 
Ford started with negative ground back in the Model T days but they changed. The basic reason was that it is an advantage to current flow. It makes a 6-volt system a bit more efficient. With that low a voltage, the system needs all the help it can get. With a 12-volt system, the extra efficiency it so miniscule that the electrical system wouldn't notice the difference.
 
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