This 1st drawing you have probably seen before. The bottom half of the drawing has a 10DN Alt plus Ex Regulator. The top half has the battery, Ign switch, idiot lamp and resistance wire. The 2nd drawing is basically the same drawing. They just stuffed the regulator inside the S! Alternator. The '60s 10DN Alt and the '70s 10SI/12SI both have 3 wires connecting the Alt/Reg to the Battery, Ign switch and idiot light. Both have a 10 Ohm resistor inside the dash harness. Both have a ACC terminal on the Ign switch.
The 3rd drawing shows a 10 Ohm 10 Watt resistor connected across the lamp because of the absence of the ACC terminal.
Some, don't add the resistor and the Alt begins to charge as it should. Some, use a bulb with lower resistance, no 10 Ohm resistor and the Alt begins to charge as it should. They also appreciate the brighter idiot light.
