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37 ground
Just can't stay away
2019/7/23 5:18
From Sarasota, Florida
Posts: 60
If I'm reading things right, my 1937 115C was positive ground. My understanding is that the positive battery cable should be connected to the chassis. My father had converted this car to 12v years ago and the negative battery cable is the one connected to the chassis. Anything special I should watch out for or take into account if and when I have to do (more likely- have to have someone else do) work on an electrical component?

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Posted on: 2019/11/27 7:46
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Re: 37 ground
Forum Ambassador
2007/4/20 17:54
From Fresno CA
Posts: 15934
There should be no issues and nothing in a stock Packard is polarity specific and would be permanently damaged if reversed. For greatest efficiency the coil should have the terminals oriented the same way the battery is grounded. If negative ground, the negative terminal on the coil should go to the distributor. Those with old original coils with the armored cable feed wire are unable to change polarity easily so their coils might not be running at best efficiency but they will still work. I would assume that with the conversion to 12v your coil was changed and was installed correctly. Likewise, the generator and regulator etc should have also been changed to 12v components and if they are working then they were installed correctly. If you are running an original 6v starter on 12v just be aware there have been many reports of cracked or broken castings on the old starters due to the increased speed and torque delivered when run at 12v. Some work for years and fail and others have failed fairly soon after the conversion. For long term you might want to consider having the starter converted if that was not already done.

It is the people still running the original 6v positive ground setups that would be most likely to have a repairman need to watch out for the correct polarity -- but again, nothing stock would be damaged if a reversal happened. Since your car has been converted to 12v, IMO it is not as big an issue because a repairman should know there would be some non stock items and at least he would be familiar with negative ground and less likely to accidentally reverse anything.

About the only thing you would need to watch out for is if the radio has had the vibrator replaced with a solid state unit or if there is a solid state power supply installed to run the 6v radio or instruments on 12v. Solid state items could be damaged with an inadvertent reversal.

Posted on: 2019/11/27 8:36
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Re: 37 ground
Home away from home
2014/7/15 11:30
From Terrebonne, OR
Posts: 2006
Typically when people convert to 12v, they also convert to negative ground. Otherwise there is no real point in making such a conversion which is often done for running modern electronics as the original 6v system was just fine and there are other, simpler ways of running 12v electronics in a 6v car.

That said and as mentioned, when I converted one of my 1940s 110s back in the '60s, I regretted it. The starter engaged so violently that I was afraid that it would either break the housing or knock teeth off of the gears!

Posted on: 2019/11/27 12:56
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