As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE REPLACING BAD AMMETER, NOTICED THE MARKINGS FOR PLUS AND MINUS WERE OPPOSITE OF THE ORIGINAL GAUGE. THE AMMETER WAS BENCH CHECKED FOR PROPER DEFLECTION AND IT WAS FOUND MIS-MARKED. WHEN INSTALLED AND HOOKED UP AS THE ORIGINAL GAUGE WAS, OPS CHECK NORMAL.