Originally Posted by db flyer
Thanks for reply. This may be a dumb question, but do you know what is the reason for a 2 or 3 wire conversion as apposed to a one? Duane
The main wire from the BATT post on the alternator to the junction block is the primary charging wire. The two wire plug on the factory alternators includes a SENSE wire and the FIELD wire that operates the idiot light. The SENSE wire also runs to the junction block and senses voltage there (as opposed to at the alternator) to automatically adjust the voltage regulator output to account for any voltage drop in the wiring. The FIELD wire actually serves two purposes. In addition to operating the idiot light, it also serves to turn on the voltage regulator at low RPMs to ensure the alternator is charging even at idle. Keep in mind that GM cuts every penny possible in building their cars, yet they kept these extra copper wires instead of using a one-wire design. Common sense should tell you that they did this for a reason.
In your case, two of these three wires already exist in the original harness. The heavy charging wire from the generator to the junction block bolts directly to the threaded BATT stud on the new alternator. The brown idiot light wire already runs to the old voltage regulator. Simply connect it instead to the FIELD terminal in the alternator plug. Now run a new wire from the other terminal in the plug to the junction block and you're done. This assumes you are using a 12SI style alternator.
You may want to consider a CS130 instead. I like to use the CS130 from a 1989-1990 Oldsmobile Custom Cruiser with 307 motor. It has 105 amp output, bolts to any 1960s GM alternator bracket, and comes with a V-belt pulley instead of a serpentine pulley. This ACDELCO 3351011 CS130 brand new is under $70 at RockAuto right now. The CS130 uses a four wire plug in addition to the threaded BATT terminal. In that case, simply connect the SENSE wire to the "S" terminal in the plug and the FIELD wire to the "L" terminal (for "light"). Ignore the other two terminals. I've had one of these in my 1962 Olds for nearly ten years now.