As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
INTERMITTENT MASTER WARNING ALONG WITH CHECK FIRE DETECTOR AND APU BLT LOW LIGHT IN OVERHEAD PANEL. REMOVED AND REPLACED APU FIRE EXTINGUISHING BOTTLE IAW DHC-8/400 AMM 26-23-01-000-801/ 400/801. OPERATIONAL CHECK GOOD IAW 26-13-00-710-801. (K)