Batt to switch to one leg of the charge light. The other leg of the charge light to Pin 1 on the alternator. This circuit needs to be switched for if not, your light will always burn as it is grounded thru R5 in the regulator. This will drain your battery.
Alternator output from the diode trio is fed into the circuit between the light and R5. This output is more than R5 can dissipate so voltage rises. Via pin one and the wiring, as this voltage rises, it finally becomes equal to battery voltage. Once this occurs, you have equal voltage on both sides of the light and it goes out. Equal voltages means no electron flow.
BTW, once the alternator starts to produce, it becomes self exciting via the diode trio.
Take a digital volt meter and watch if battery voltage steadly climbs after starting. It will bump up by a tenth of a volt or so as the batt is recharged. It should finally settle out at the regulator's voltage setting as it becomes fully charged. If it does this, you have a wiring problem, not an alternator problem.