Incorrect battery polarity issue.

chrisabes

chrisabes

Member
I recently purchased a 1928 Pheaton that has been extensively rebuild, looks wonderful. Earlier today I was replacing the instrument panel light when I realized that the polarity is incorrect. The earth is Negative. I should mention all the electrical components are working eg. starter, charging system (generator), lights horn etc.
My question is this. If I change the battery cables to their correct battery (6 volt)terminals, ensuring a Positive earth, what systems would be effected? My main concern is the ignition and charging systems.
Any advise would be most welcome.
 
The coil wires have to be switched, the amp meter wires switched, and I think the generator has to be re polarized. You get more info tomorrow, I'm sure.
 
Could the best solution to be to leave the car as you bought it ?

Switching to a negative ground system was a chance that was recommended if you installed a radio in your Model A so it was not uncommon to have a Model A with a negative ground system.

Note : Information I have read does say that the generator works "better" with a positive ground system.

Marc
 
I would change to the positive ground because that's the way it was made and what everyone would expect to find if they offer help for a problem. Just switch the battery around, then jump the 2 cutout terminal for one half second to polarize the generator. Now turn on the lights with the engine off and see if the ammeter reads discharge. If it reads charge, then switch the wires on the back of the meter.

Also check the coil polarity to see if it's correct. If it's not correct just change the wires on the primary terminals around.

The chicagolandmgclub has an excellent short description on checking coil polarity. Do a google search for "coil polarity" and you'll find it's the first or second listing.
 
Chiefs' family cars' ammeter was hooked backwards, he just left it that way for LAFFFS! Once he used it as an "excuse", NOT to have to take a Guy to town, "LOOK, my generator AIN'T working"!
Bill W.
 
The battery was in backwards on my roadster. It ran fine, but when I installed LED tail lights, they would not work. Eventually I figured out the battery was in backwards. I turned it around, repolarized the generator and was good to go.
 
Hi Manager, we live on Tamborine Mountain and the vehicle is a 1928 Pheaton as mentioned on my first post. See attached.
Updating on the battery polarity issue. Thanks to the post replies, I have been able to get it all sorted. The generator worked without re polarizing it, the coil terminals were checked using a pencil and the amp meter wires were switched to indicate a charge.
 

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The1929 Fordor I recently purchased was also converted to negative ground at some point. I would like to go back to positive ground. This may sound dumb, but don't DC motors turn in the opposite direction if the leads are switched?
 
Coneross-A

The model a starter is a series type DC motor. What this means is that the field winding is in series with the armature. So, the motor turns the same way for positive and negative ground cars.

The series type of motor was used because it develops a large amount of torque when it isn't turning. As the speed increases, the amount of torque drops. Thus, it has the high torque when it needs it..to start the car.

For a shunt fed motor, the direction would change if the leads where changed in polarity. Also, the torque isn't as large when it isn't turning. So the shunt fed motor isn't ideal as a starting motor.

Ford used the series fed motor because it is the best as a starter for the engine, not because it could be used for positive or negative ground electrical systems...that's just an extra benefit.

Marc
 
chrisabes said:
Hi Manager, we live on Tamborine Mountain and the vehicle is a 1928 Pheaton as mentioned on my first post. See attached.
Updating on the battery polarity issue. Thanks to the post replies, I have been able to get it all sorted. The generator worked without re polarizing it, the coil terminals were checked using a pencil and the amp meter wires were switched to indicate a charge.
Click to expand...

Great to hear!
 
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