88 ranger melting wires for alternator

[Ajbdad]

My 88 ranger with a 2.3 keeps melting the amp gauge shunt wire. The truck surges at idle if I unplug the alternator it smooth out. Five unplugged the dash and it hasn't blown any fuses or fusible linked. I've changed the alternator and battery. Need help have to fix for work on Monday.

Thanks in advance