Just need to simulate that charge direction limitation thing with a simple LED Light Emitting Diode. I bet you could wire it to the ignition side and get it working without the clutter called the instrument cluster. Could be a real simple diode in a socket that snaps into the dash. On with ignition and off when the alternator runs.
What do you think Libby? Does he need a resistor on the LED to take the 12 VDC as well? I think so just not sure of the ohm rating. similar to what is used when folks mod their dash lights using LEDs.
I used a light bulb from an autometer gauge. I tried the LED thing once and it didn't work.
With LED on 12v you need 1.2K resistor,but I only know bulb one.