As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHEN NR 3 LOOP-B IS SELECTED MASTER FIRE WARNING LIGHT AND BELL ARE CONTINUOUSLY ACTUATED. LIGHT AND BELL ARE TERMINATED WHEN LOOP-A IS SELECTED. T/S RANG OUT EACH SECTION OF LOOP WITH METER AND NO DEFECTS NOTED. CLEANED AND RESECURED CONNECTORS AND SYS OPS CK'S GOOD PER MM REF 20-10-1.