As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RETURNING TO BASE FROM SCENE CALL FIRE WARNING AUDIO GONG SOUNDED INTERMITTENTLY. REMOVED AND REPLACED FIRE WARNING UNIT PN L315M5007051 RMVD PL650 INSTALLED PL107, SYSTEM FUNCTIONAL CHECK SATISFACTORY. APPROXIMATELY SEVEN MINUTES AFTER DEPARTURE FIRE WARNING GONG INTERMITTENTLY ALERTED, ABORTED FLIGHT RETURNED TO BASE. PERFORMED INSULATION TEST FWD DETECTOR PN 3119366-01 AND AFT FIRE DETECTOR PN3119367-01, FWD DETECTOR FAILED TEST INSTALLED SERVICEABLE FWD DETECTOR PN 3119366-01 SYSTEM FUNCTIONAL CHECKS GOOD.