platt-deutsch

Neg Ground or Pos. Ground

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I am putting diodes in the Ness Starter boxes and I just noticed the printing on the back plate at the battery terminal is stamped " + battery"  The wiring diagrams I have looked at on the 1925 era DBs all show the Positive terminal of the battery going to ground (positive Ground) so why would they stamp the identity of the battery terminal with a Positive? 

I have always connected them Positive ground but now am wondering why they would stamp that terminal + when it should be stamped - ?

This will depend on what type of diode I will use, case anode or cathode.

If someone hooks the battery up as negative ground the starter/generator will of course start cranking the engine if I put the proper diode in for positive ground.

Do most of you have them connected positive ground as the wiring diagram shows. With the old cutout relay it didnt make any difference unless yiou are using a pertronix ignition module in the distributor.

Thanks

Edited by platt-deutsch
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Platt, The quick answer is the Dodge Brothers used NEG ground from the beginning up to circa '23 roughly when the horn button was removed from the driver door (operated by the knee) to the top of the steering column. Then the switch to (still 12v) POS ground which continues into the 6V series and on up to the '50s. I hope this helps. Rodger "Dodger"

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Rodger, I know the switch to positive ground on the single-unit cars occurred sometime around when the horn button was moved from the door to the steering wheel, but I don't think it was simultaneous.  I have a highly-original late '22 model (high cowl) made in November of 1922 that has the horn button on the steering wheel, but still had negative ground (confirmed by the original instruction manual that came with the car).

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I THINK that is what Rodger means by circa '23. The story is they changed location of the horn button and experienced corrosion on the contacts. SO they changed polarity to cure it. So there could have been cars built with the button moved but still negative ground. As usual no two DBs are the same. 

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My '25 is hooked up as positive ground.  The battery cable (assuming it is original) seems to support this since it would be a little short to reach the other side of battery box.

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IIRC, in his summary of plant manager Frederick Haynes's production records and notes, Don Butler discusses exactly when they switched over to positive ground.  I'll try to find it.

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Actually the answer appears in the 1928 Master Parts Book reprint.  On page 203 it says the horn button was moved from the door to the steering column with car no. 705679 on or about April 15, 1922, but the electrical system wasn't changed over to positive ground ("reversing battery in battery box") until car no. 780960 during the first week of October, 1922 (page 208).

 

So according to the Master Parts Book between April 15 and only early October, 1922  the cars had a 12-volt negative-ground system but the horn button on the steering column; however, my car (no. 807012, produced during the third week of November, 1922) seems to have had a negative ground system, too, according to the way it was set up and the instruction manual that came with the car, which I was informed by the previous owner's daughter, and had every appearance of being, the original.

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For what it's worth, I have a 2nd Series 1922 built in July, 1922. The horn button is on the door. It's negative ground now. Serial # is 746880, Motor # 800948. It's pretty much original.

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