First try removing the voltage regulator and making sure it has a nice shiny metal to shiny metal contact to the body. Resistance on the ‘ground side’ of the circuit can cause just as much trouble as resistance on the positive side. Next wait for some of the electrical experts to respond. There...
Hot amp meters from to much current going thru them have caused fires. Somewhere on this forum is a schematic for wiring in a relay triggered connection between the battery or alternator ( @67Dart273 correct me here) and the voltage regulator to limit the overcharging caused by voltage drop...