I&M Electric

12 Volt – 60 Amps

The Delco alternator is designed to operate using more than one wire going to the vehicle electrical system. In fact there were originally at least 3 wires. One BAT, one field and one sensing. Actually the field wire goes to the “idiot light” and then to the ‘RUN’ position of the ignition switch. The sensing wire either goes to the ‘BAT’ side of the ignition switch or the ‘RUN’ side depending on the application. When the ignition is in the run position the sensing terminal is energized with battery voltage and the field terminal is energized with a current limited voltage through the lamp. When the alternator starts charging, the field voltage raises and the voltage differential across the lamp reduces and the lamp goes out. The charging voltage is ‘sensed’ through the sensing wire and the internal voltage regulator regulates the voltage to about 14 volts.

When used in the one wire configuration, the sensing wire is connected directly to the BAT terminal. The field terminal is not connected. If the engine is run at a high enough rpm the regulator will “leak” enough voltage to the field to energize it and the alternator starts. The trick is to get the regulator to “leak” at a lower rpm, and thereby “self energize”.