70 duster not charging .

Anything in the engine bay switched by the key should be right at battery. Otherwise you have voltage drop. but that close to 12 should not stop it from charging, if VR and alternator are good.

I've posted this before. The "usual suspects" are the ammeter wires and the ign "run" wire going through the bulkhead connector (so at least 3 terminals possible) as well as the key switch connector and the switch itself.

and what year is your car? Newer models, 72? 73? have an annoying white connector where the engine harness goes to the firewall. Those are a known problem. Cut it out of there, and permanently splice the wiring together.

Otherwise, consider a relay to "fix" the problem. Locate and cut your "run" wire coming out of the bulkhead connector. Feed the firewall end to trigger a bosch relay, and connect the engine bay cut end to the switched contact. Feed the relay contacts with about a no12 fused or breakered, from the start relay "big stud."

Doing this ALSO fixes "over charge" (overvoltage) caused by harness voltage drop