As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AURAL FIRE WARNING CAME ON APPROX 10 MINS INTO FLIGHT. COULD NOT EXTINGUISH. PROCEEDED BACK TO EWR FOR AIR RETURN. FOUND AURAL WARNING FIRE GOING OFF CONSTANTLY. REMOVED AND REPLACED M1000 PRINTED CARD. ALL CHECKED GOOD WHEN C/B WAS RESET, AFTER CARD REPLACEMENT. PERFORMED FIRE TEST AND ALL CHECKED GOOD. ROTABLE PARTS CHANGE WAS INDICATED - TT 1423811, S/N OFF 01645 UNIT, PRINTED C OFF 99-3151-9-9004 1645 ON 99-3151-9-9004 1768.