1966 Ford Thunderbird voltage regulator harniss

http://www.justanswer.com/classic-cars/3h9b8-proper-wiring-1966-ford-thunderbird-alternator.html go this site for a diagram

"I" is "ignition". That will have battery voltage when the ignition switch is on.

"A" is the 12 volt feed circuit where system voltage is monitored. It will typically have full battery voltage all the time.

"S" is "stator". That wire goes to the terminal on the back of the generator with a white insulator. It will have half of battery voltage, about seven volts, when it is working. Ford is one of the few manufacturers that uses that to turn off the warning light on the dash.

"F" is for "field". That wire goes to the back of the generator with the red or orange insulator. Current flows through the regulator into that terminal, then through the spinning rotor to create the magnetic field. By varying the amount of current from 0 to 3 amps, it controls the strength of the magnetic field and therefore the amount of output current and voltage.