The Stovebolt Site Forums The Shop Area The Electrical Bay Positive ground Why???

After reading the post about the 39 GMC and its battery question, it got me to thinking. Why did they make some trucks and cars with positive ground?? What is the advantage of this other than throwing sparks when jump starting it with out knowing the difference? Joe

The only reason for positive grounding that I have heard is that there is less battery corrosion with positive grounding, but I do not even know if that is true. Apparently it was a very common practice back then to put generator-equipped vehicles with positive grounding.

the majority of the pos ground systems were fomoco, tho there was some Brit &/or Euro that way too - supossedly something to do w/ making spark plugs last longer, which may have been a problem back when.
don't hold it to me, but methinks pos ground was F ords lawyers way to get around some GM patent.

Bill

All early Jags were positive ground. Doesn't power flow from neg to pos? Maybe the thought was to provide a more direct or controlled current carrying path to the potential point...

I don't know why the started off with pos grnd, but automakers switched to neg groung to try and slow down some of the body rusting problems.

I had a 55 dodge truck that was also positive ground.

Gobsow, you are correct that electrons flow from (-) to (+). I suspect that is the reason for the switch to negative ground, as the principles behind electrolytic rust removal should apply to an electron-rich chassis. However, the distance between theory and practice is sometimes measured in buckets of bondo. :p

I'm curious if there is another benefit in maintaining a potential in the chassis, perhaps battery life is improved? Anyone who didn't fall asleep in Electrical Engineering 101 is welcome to jump in with corrections/clarifications.

Let the electrons flow

The issue seems to be that of electrolysis/corrosion.This may shed a little light on the subject. http://engr.smu.edu/~levine/ee8302/positiveground.pdf

Maybe one reason the 1939 GMC trucks had Pos ground, was so they could sell them to the Brits thru Lend-Lease? My dad used to have a '59 Jag Mk IX -- that beast couldn't hold a charge. I learned why the English drink warm beer -- Lucas Refrigeration!

Joe H, Mack trucks used to have positive too. Why, I don't know. But I do know it would smoke the diodes in a CB radio in a heart beat if ya forgot about the positive ground. Mike

Thermodyne64, Thanks for the link

'248,anytime.

We had Positive Ground in the same context that the Germans had to drink warm beer. If any of you have ever had a vehicle with Lucas electric you will be able to relate. The two different systems are in part related to the two theories of electricity as mentioned above. In the end it really doesn't matter neither proved to be better than the other.

**** engineers liked the positive ground electrical systems and because they were the largest automaker during the early years, many smaller companies followed suit. In the late 1940' when GM became the largest auto manufacturer engineers at GM belived negative ground was best. Because they were in charge so to speak (sorry, I had to work something in) they led the way. In addition GM made many of the electrical compoents for the independents, so...the independents had little choice to to conform.

The important thing is that you do not install any modern solid state accessory designed for negative ground....into any positive ground system. The results will not be pretty....Randy

One reason I was told was that since the earth is positive ground, some engineers wanted to keep vehicles the same. This is one subject we did not cover in electrical dymanics.

I think it's just because it's nicer to have a
"positive" system than a "negative" system.

http://www.positivepress.com/news/

Murph
...............___
_=======| :p \___
|(.....)_(O)____(....)c
...(O)...............(O)
'49 GMC 3/4

As many of you know, my dad has a 1930 Fjord AA stakebed. According to the Model A guys, Fjord went to positive ground (I think some early Model Ts were negative ground, but I may be wrong there) due to the battery corrosion issue. After a while, the battery manufacturers started making better batteries, so it became a matter of preference. Eventually Chevy's negative ground system took over. My dad and I learned the hard way about the A's positive ground system - we killed an old POS battery charger when we hooked it up backwards. Like many things, there was a reason at one time, then it took 20+ years for everyone to get on the same page (6-volt GMC trucks, anyone?).