positive ground A

Jim Turner · Dec 1, 2011

Can someone tell me what is affected when a tractor designed for a positive ground (1949 A) has the battery connected as negative ground? When my A would not start, I was looking through the manual and discovered the battery in my A was in backwards, I suppose for the three years I have owned it plus some. Wouldn't the starter turn backwards? How would that work? thanks, jim

Greenday · Dec 2, 2011

The first thing that it usually does is burn up the voltage regulator. The starter will still turn the same direction.

John T · Dec 2, 2011

Your tractor, like ALL JD Two Cylinders, were originally positive grounded. A genny can still charge at EITHER Polarity but if its not polarized the same as the battery (Pos or Neg ground) you can fry the Voltage Regulator, thats why one Polarizes it BEFORE start up. If polarity is reversed, an ammeter needs its leads swapped or it will read bass ackwards and similar if its a coil distributor ignition (not a mag) the coil leads should be swapped for the most efficiency.

Your starter will still turn the same direction REGARDLESS of polarity.

John T

BushogPapa · Dec 2, 2011

I always thought that the Headlights would shine DARK Black..sucking IN light instead of shining light OUT, if the polarity was backwards...!!!

But, seriously...

Are you SURE it has not been changed to a Neg ground system..??

Ron..

gtx1967jewison · Dec 2, 2011

It actually will run either way. U just have less spark due to coil polarity. Starter & lights don't care.

John T · Dec 2, 2011

Yep when he said in his post

"When my A would not start, I was looking through the manual and discovered the battery in my A was in backwards," sounds like it got converted (correctly or not who knows), I tried to explain to him what happens and the differences and what needs done like coil polarity and genny polarization and ammeter leads and starter direction etc. etc.

Hopefully he will figure it out now

John T

gtx1967jewison · Dec 2, 2011

It actually will run either way. U just have less spark due to coil polarity. Starter & lights don't care.

Walt in Jaxn Tn. · Dec 2, 2011

Ron, that's called a "black hole"

Jim Turner · Dec 2, 2011

How would I tell if the polarity has been reversed. The only thing I can see is that the ammeter has been disconnected.

John T · Dec 3, 2011

You can tell if the polarity has been reversed by looking at the battery and seeing which battery post is tied to frame ground, Positive like original or Negative if its been reversed..........

I cant tell you why the ammeter has been disconnected (maybe they reversed battery polarity and didnt like to see it working backwards) BUT I CAN TELL YOU UNLESS THE WIRING WAS MODIFIED THE GENNYS OUTPUT CANT EVER GET TO AND CHARGE THE BATTERY (via the ammeter as normal) IF THE AMMETER IS OUT OF THE CIRCUIT.

John T

Late A Wiring Diagram

positive ground A

Jim Turner

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Greenday

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gtx1967jewison

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Walt in Jaxn Tn.

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Jim Turner

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