The only thing you need to do to use a positive ground generator in a
negative ground application or visa versa is to make sure the field winding
is polarized correctly. To do that momentarily touch either +12V or -12V to
the field connector (smaller of the two connectors). For a negative ground
system you touch +12V, or you touch -12 for a positive ground system. You
should always do this anyway when installing a new generator since you don't
know which way it had been polarized. Neglecting to perform this operation
causes a large current spike the first time you turn on the car which can
cause damage to the voltage regular, ammeter, etc.
Good luck!
-----Original Message-----
From: Simon Favre [mailto:simon@mondes.com]
Sent: Wednesday, May 02, 2001 7:23 PM
To: Paul
Cc: Vintage Race
Subject: Re: Positive ground alternator?
Are you sure it's an alternator? 1964 sounds like it should be a generator.
If you know some basic electronics, and have the right schematics, you can
use a negative ground generator to produce positive ground current, and
vice versa. A generator doesn't know the difference. In the usual generator
circuit, it's the generator light that "polarizes" the generator. Anything
else is hocus pocus. The regulator and the generator are usually matched to
each others max ratings, so mixing and matching brands there can be
dangerous. I used to have a Lucas generator (positive ground) happily
putting out negative ground in an Alfa Spider that also didn't care which
polarity it was fed.
Alternators are polarized by the way the diode chassis is mounted, and they
are all negative ground, AFAIK. There is no easy way to change the polarity
of an alternator.
Simon
Paul wrote:
>
> I'm looking to replace a positive ground alternator in a 1964 Datsun
1500.
> Since Datsun never brought too many of these little cars in to the states,
> finding parts is rough. Does anybody know of another car that was
imported
> that used a positive ground alternator? I seem to remember burning up one
> in a 1970 Ford Cortina by wiring it backwards to the battery. Were they
> positive ground or is my memory finally gone too!
>
> Paul
> Ohio Roadster Owners Club
> Sloan Racing
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