Electrical gremlin
This is the 3rd thread on the same subject in about a month. The corrosion is due to a water leak, wiper pivot or windshield gasket. Replacement gauge or placing both wires on one stud isn't a fix. Bolt the wires together off the gauge? Since the same water leak damages the headlight switch also, fix the water leak. Consider a handmade shield cut from butter tub, milk jug, whatever.