Here is what my shop manual covers the operation, this follows the diagram from the link in my manual. I'd scan it but my scanner died.
Circuit Operation: With the Ignition Switch in Start or Run, Battery voltage is applied through the Gage Fuse and the Generator Warning Light to terminal L (brown wire) of the Gernerator on models equipped with warning indicator. The 40 ohm Resistordraws current and the Warning Light glows. Current flows through the Gernerator Field Winding. On models with optional Gages ("A" Series only) initial voltageto the generator is provided through the 10 ohm resistance wire.
The rotatingfield and the rectifier diodes produce a DC output voltageat the BAT terminal. DC voltage ia also appliedto the field winding, through the Diode Trio.
Whenever the generator output voltage is low, the regulator increases the currentin the field winding. This causes the output voltage to increase.
Field current is provided by the Diode Trio or from the Battery through the Generator Warning light.
At low engine speed, current flows from the Battery through the Generator Warning Light to the Field Winding. The Generator Warning Light is lit whenever the Battery supplies field current. As the engine speed increases the Generator output voltage increases and the field current is supplied by the Generator through the Diode Trio. When the voltage on each side of the Generator Warning Light is about the same, the light goes out.