As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FIRE LIGHT ILLUMINATED WITH THE APU SHUTDOWN. CREW REPORTED THAT AFTER TAKEOFF THEY HAD APU FIRE WARNING INDICATION WITH THE APU SHUTDOWN. CREW DISCHARGED APU FIRE BOTTLE. APU FIRE WARNING INDICATION WENT OUT THEN BEGAN TO FLASH AND CAME BACK ON STEADY. PERFORMED TROUBLESHOOTING OF APU FIRE WARNING SYSTEM AND FOUND APU FIRE DETECTOR M334 WITH LOW RESISTANCE. REPLACED DETECTOR M334, APU FIRE BOTTLE. APU FIRE DETECTION SYSTEM TESTED NORMAL.