Folks,
I think some of the confusion comes from the fact that folks are using
different types of alternators.
A GM (i.e., OE for something general motors) alternator is NOT a single
wire unit. You must make at least two connections to the alternator. The
obvious is the charge line (commonly referred to as the white wire and at
the very least it should be supplimented due to the increased charging
potential - don't forget to protect or scrap the ammeter).
The second which I believe is the source of a lot of confusion on this
list is: The field wire. For an OE application GM alternator you must
supply the field coils so that the alternator can produce a charge.
Be careful with the field wire. One might think you could just run it
from the unswitched power at the battery. If you do, the roadster won't
respond when you remove the key - she'll keep right on purring.
Basically, the circuit will reverse and power the ignition stuff through
the alternator. Make sure the line is switched, and you might add a diode
for good measure.
That said, I believe many of you are using aftermarket alternators sourced
through outfits like summit or pegasus or JC whitless or ... It is
possible to purchase a true single wire alternator. And, it may be called
a GM "type" alternator because the outer case dimensions mimick the GM
units. But, it is different in that it will either be switched internally
(such that it pulls a field backward through the charge circuit as it
starts spinning) or it will have fixed magnets in the case supplying the
field.
So, to repeat: for an OE Application GM alternator - you will need to
make two connections. The available GM harnesses have 4 leads - 2 are not
necessary to produce charge. I recall that the fat wire makes the juice.
Sorry, but I can't point you directly to the field wire (unless you want
to talk Bosch conversions).
FWIW, my experience with GM alternators has not been good. I will admit
to driving a competition level stereo, A/C and driving lights, but 85A
should have been plenty. Even in their OE applications, the late style GM
alternators die biannually (ask the service techs). I got tired of
getting warranty replacements every 4 months and forked over the cash for
a Bosch alternator. I only bought 1 and never had to make a warranty
claim.
Since I want to move the alt to the passenger side of the motor, and I
have none of the brackets folks have described to accomplish the task, I'm
planning to just fabricate mounts for a bosch unit. Cost twice as much
out of the box, but less than half the headaches.
And, if you are feeling adventuresome. Some of the older Fords do use
true single wire alternators if this is what your after.
Good luck,
Milton
Enjoys his tunes
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