Re: Alternator help needed...1-wire / field wire to batt. stud trick

[Jerry Casper <gremlingts@xxxxxxxxx>]

--- farna@xxxxxxx wrote:
> An alternator has to have some battery voltage going
> to it to excite the field before it will charge. A
> standard Delco alternator can be made into a
> one-wire by simply attaching the field wire to the
> battery cable stud on the back of the alternator.


 Uh, two things...a single-wire alternator has a
SELF-exciting regulator, which doesn't require a field
voltage to get it to start charging, just a higher
potential from the alternator turning over at a higher
rpm. THis is NOT the same thing as a standard
alternator!
 The OTHER thing is that if you jumper a normal GM
style alternator Field winding wire to the Battery
stud, this will cause your battery to discharge more
quickly over time, as you are keeping a constant ( if
tiny ) electrical field in the field circuit, and if
your car sits a couple of weeks, it could be dead by
then. How do I know? I did this with my '57 Chevy
years ago, when I upgraded from a generator to an
alternator, and instead of finding the correct wire
from the key switch, I just jumpered it. Sure, it
works...but you will discharge your battery , too. If
you don't let the car sit for weeks, it's fine, but if
you go away a few weeks, and come back, dead or low. I
lived a few hours away from where I stored my car, and
would only come back on weekends and drive it. If I
missed a weekend, it'd be 2 weeks. I learned quickly
that bypassing the shut-off circuit for an alternator
field circuit wasn't a good idea. 
 "Maybe" the more modern GM alt's are ok with it, but
they still are NOT 1-wire with self-exciting
regulator. Those are different than a standard 3-wire
alternator.  Here's a link describing how the 1-wire
is WORSE in performance than the older 3-wire
alternator, you read it and decide for yourself..I
just did, for the first time, and some of the info is
new to me. Just a thought before you convert...the
1-wire has LESS ability to sense voltage use than the
standard 3-wire, and can cause weak voltages! Check it
out at :

http://www.madelectrical.com/electricaltech/onewire-threewire.shtml

 Ok, that's my contribution, you make your own
decisions after doing some research. Looks like the
3-wire 12si GM alternator DOES use Battery-to-field
connection in the MOdel T picture, so maybe these
don't bleed voltage to the field coil as much as the
older ones I used on my '57 Chevy did. learn sumthin'
new ever' day...

Jerry Casper


		
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