Plymouth PA Polarity

[broker-len]

in the Plymouth 4 cylinder owners guide first edition July 1931 shows a wire diagram where the negative is grounded    second edition  December 1931   shows the positive as being grounded    I have a 32 PA and it had when I got it ,,I think,, positive ground,,,,  my question is----does it matter  to the starter and generator which way you are running   why through the years has BATTERY POLARITY kept changing

[Oldtech]

Chrysler products generally used positive ground until alternators came along.  It doesn't matter a lot. There are regulators for Pos and regulators for negative but  a PA won't have a regulator - at least not originally. 

Why is another question.  Generally electrical circuits use positive logic. That is, things run from positive through the circuit and back to the negative terminal. Sometime in the history of the world they discovered that electrons are what is doing the work. These are negative particles, so some engineers decided that if the flow was electrons it must be from negative to the positive. This is likely true but,,, it's basically irrelevant. The electronic world is back to positive logic.

 

The starter doesn't care. The generator needs to be polarized to whatever system is used. Just apply power to it for a jiff to magnetize the field blocks. The  amp meter will read backwards if you hook it up reversed. 

Easy way to tell what it's supposed to be. Put a battery in it and turn on the lights. If it reads discharge good, if it shows a charge ( engine stopped) you are backwards.

[broker-len]

thanks for the info,,,,As the teck advisor for Plymouth Club,, I had some one contact me with the question because , as I said the first owner's book showed negative ground ,,I have all the manuals but never noticed ,,so I was not sure what to tell him

[nearchoclatetown]

Could the change have had anything to do another change? Dodge Brothers were negative ground from 1914 until they changed the location of the horn button from the door to the steering wheel in 1922.  Factory bulletins tell us there was corrosion on the contacts of the horn button and the change was to end that. So the first few months of the horn button being on the steering wheel they were negative and corroded. Could there have been a similar change to Plymouth?

[m-mman]

More modern car but years ago I had a 1955 Mercury with the symptoms that the radio would work only with car running and the battery cables disconnected(?) 

 

Car was factory 6 volt positive ground, but somebody installed a new battery and polarized the generator for negative ground. everything worked but the radio.  Cant remember today what the amp meter was showing, it must have been backwards.

 

Swapped cables, repolarized and everything was fine.