72 Dart Swinger has melted wiring under dash?

one possible issue that my car had was the amp meeter gets rusty from the wiper pivot seals leaking onto it. This causes a massive voltage drop. A easy test is to use a voltage meter and test the voltage going into the balast resistor with the key on and see how close to the batter it is. If it is within 1 volt then it should still work that is not the optimal volt drop but should be usable to find the problem