[Rick Parker]

Are you using a separate voltage regulator? If so, the light is controlled by the action within the remote mounted regulator. One side of the bulb gets power from a switched 12 volt source (or direct from key switch) and the other side is grounded by the regulator after passing through the fuse panel or being connected directly to the regulator. When enough current is created by the excited alternator, the circuit grounding the bulb is switched eliminating the ground and causing the illuminated bulb to go out. On the old voltage regulators, this was done with a set of mechanical points and electromagnetic energy, on the new regulators, transistors do the switching.