Denny Graham,
There is no external regulator. This stuff pertains to a system that has been changed to a internally regulated Delco 10SI alternator.
On a three wire setup, the internal regulator has two connections to the outside world through a external plug..the DA plug. These two connections allow the regulator so see system voltage and allow it to be energized with voltage from a outside source when the engine is started so as to get the whole enchilada charging.
Through some mysterious circuitry, the #1 wire completes a circuit to ground which energized the field and allows the charging process to begin. When the alternator starts creating power, this ground (#1) changes to a positive source of voltage and the wire now produces power...enough to power the ignition on its own, which would preclude turning off the engine if it were wired directly to the coil. The diode prevents the reverse flow of voltage to the coil.
After the alternator starts charging, #1 is powered as long as the engine is running. If you turn the key OFF but #1 is supplying the coil then it's as if you didn't turn the key OFF.. does that make sense? This is what this little diode thing is all about.
I flunked electronics so this is merely a shade tree explanation of how it works, and it's my shade tree explanation to boot! Caveat emptor!
Stuart
