As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FIRE HANDLE LIGHT ILLUMINATED AT CRUISE WITH NO AUDIBLE BELL WARNING. APU FIRE SWITCH PULLED AND ROTATED. FIRE BOTTLE DISCHARGED. APU WAS NOT RUNNING. REPLACED APU AND ENG FIRE CONTROL UNIT, CHECKS OK. REMOVED AND REPLACED FIRE BOTTLE PER MM VERIFIED DISCHARGE NOZZLE FREE FROM OBSTRUCTION, VERIFIED RESISTANCE LESS THAN .0025 OHMS SQUIB TEST GOOD.