As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, CLIMBING THROUGH 15,000 FEET, THE LEFT FIRE WARNING LIGHT CAME ON. THE PILOT RETURNED AND LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED THE AIRCRAFT AND NO EVIDENCE OF FIRE WAS FOUND. THE FIRE WARNING WAS CHECKED FOR PROPER OPERATION AND CHECKED GOOD. MAINTENANCE WAS UNABLE TO DUPLICATE THE PROBLEM. THE AIRCRAFT WAS IN A HEAVY RAINSTORM PRIOR TO THE FLIGHT, AND SUSPECT THIS CONTRIBUTED TO THE FALSE INDICATION.