As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU INTERMITTENTLY DOES NOT START ON BATTERY POWER. PERFORMED AN APU BITE CHECK FOR CURRENT FAULTS. FOUND MAINTENANCE MESSAGE 49-41248. TROUBLESHOT THE SYSTEM DOWN TO THE START CONVERTER UNIT USING THE FAULT ISOLATION MANUAL. REPLACED THE START CONVERTER AND OPERATIONAL CHECK NORMAL.