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S.O.S. - ASAP need help with battery


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Hi. I am a new owner of a 48 roadmaster and am putting a new battery in after many botched attempts with non workin 6 volts, delivery of 12 volt instead of 6 volt etc.

Now my mechanic is asking me if the original system required a negative ground 6 volt or a positive ground 6 volt. I have been assuming it was a positive ground, but he is wondering if perhaps it is actually a negative ground as some cars did have that back in 48. Please help!! Thanks :)

Edited by roadmistress (see edit history)
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roadmistress, welcome. Do you have pictures of your Roadmaster?

May I be the first to invite you to join the Buick Club of America? Buick Club of America - BCA - Welcome .


HI Ben,

Thanks for the warm welcome and all the good advice. Yup, we figured out that the last mechanic had provided us with a 12 volt instead of a 6 volt and then my dad it in backwards. I then drove it and it did some damage. Luckily we have her in good hands now, with a guy who realized right off the bat that it was a 12 volt and that he was pretty sure it was a negative ground car. :D

Here is a photo,( not a very good one ) of the Roadmaster, with a friend and my dad putting the battery in backwards :rolleyes:


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  • 2 weeks later...

IF the prior battery installation was "backwards" . . . AND the car still has a generator (not an alternator or a generator case with alternator guts) . . . THEN the generator will need to be re-polarized for the appropriate negative ground situation.

Having the generator polarized, by installation of the battery for + ground rather than - ground, will cause ignition coil output to be decreased, which can cause some spark plug fouling situations, which can mean deteriorated engine performance. The decreased spark plug firing voltage can give similar symptoms as a flooded carburetor, or a carburetor that is running very rich (mixture-wise).

Welcome and enjoy!

Please keep us posted.


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