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Old 03-15-2011, 03:36 PM
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Three-Wire Delco 10SI/12SI Alternator Question

There's a lot of information out there about the three-wire versus one-wire alternator setup, and I'll just share this:

One-Wire versus Three-Wire

Explanation of how the idiot light circut is wired and how it works.
GM 3 wire alternator idiot light hook up

Explanation of how the voltage sensing circut is wired and how it works.

And a picture of the wiring using a 1N5408 diode and NOT using the voltage sensing circut.

While the picture suggests a 10-guage wire from the alternator stud, my perference is to use 8-guage wire. And rather than pig-tail the voltage sensing line to the stud, I run a wire to the feed stud of the fuse panel so I can atually get some value from voltage sensing.

Anyway, enough sharing. My question is this:

In all I 've read it's not been clear whether any Delco 10SI/12SI can be used in three-wire mode just by connecting all three wires or if only some of the built-in regulators are capable of doing it.

What's the answer?
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