71 Dodge Dart Swinger in England

Schematics and ammeter gage mod. I added a 12v LED for a fault light. Used a #50 drill and some JB weld epoxy to glue it in. This makes it look somewhat hidden when not lit. Being that the LED is polarity sensitive, the red hot wire for thr LED i soldered to the input side of the volt gage guts, the black output wire will go to the L terminal on the alternator. In a fault situation the voltage regulator in the denso shunts to ground turning the light on, or on startup the fault light will light up until alternator comes online. Usually a second or 2.

Diagram B is what you should wire it to be. Diagram A is stock wiring. Notice how all the alt output in diagram A goes through the bulkhead and inside the car to feed the ammeter then it goes to the battery. This was marginal back when these cars used a 20amp alternator.

If you mod the ammeter gage to volts it only needs an ign hot sense wire, and chassis ground. This is way safer than the old ammeter gage.

I hope this helps
Matt