As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, THE FIRE WARNING LIGHT ILLUMINATED. ACFT WAS IMMEDIATELY RETURNED AND LANDED WITHOUT EVENT. MAINTENANCE FOUND A BAD FLAME DETECTOR, PN: 92310-04802-105, SN:5853 REMOVED, INSTALLED SN: 4565. THERE WERE NO INDICATIONS THAT A FIRE HAD OCCURRED, ACFT RETURNED TO SERVICE.