You did it "correctly". You have hooked up the sensing wire. You need to hook up the other blade to a bulb, thru the bulb and to ignition source. This would be the alternator exiting wire. Everybody here is right about the wiring EXCEPT many "One wire" alternators sold or modified are made using a SI (System Integrated) CASE! So they look like a normal SI.
The original SI is known as a three wire alternator. There were three wires leaving the alternator in the original GM system. Then a new three wire scheme was borne, but it's really a two wire. One of them attaches the alternator to itself. That little guy is a wire from the famous "blade" terminal 2 and goes to the battery stud on the alternator (that's the sensing wire). That works OK on our old trucks with little or no accessories. So only two wires leave the alternator: The battery wire and a wire from the famous "blade" terminal no.1 to a idiot light, thru light, to ignition switch "ON" terminal, which provides necessary resistance and glows if we are not charging properly. (This is the exciter wire). If you don't care about having an "annunciator" light, just wire no.1 to ignition "ON". ACC....or to an ignition terminal not connected to anything else.
So to be technical. The only "true" one wire alternator is one you buy that is a one wire alternator. They "self excite" and "sense" internally/electronically. These one wire alternators supposedly have a different internal voltage regulator.
The reason the indicator lights is that if alternator is working it sends 12V to one side of bulb. The other side of bulb has 12V also, from ignition switch source. As voltage drops on one end due to low alt output, the bulb starts to glow/come on receiving less than 12V on one end/getting grounded. Voltage drop causes it to light. It will also light when key on (bulb check), until the dynamo spools up.
Fin
Last edited by bartamos; 06/27/2025 10:34 PM.
