As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAULT LIGHT CAME ON DURING START USING BATTERY. GROUNDED - YES. PER B737-900 FIM 49-60 TASK 801, 819, 822 APU FAULT HISTORY HAD MULTIPLE HITS OF 49-41249 START CONVERTER UNIT SHOWS LOW BATTERY POWER. MAINTENANCE HISTORY PAGE HAD MULTIPLE HITS OF 49-41297 START POWER UNIT SHOWS INTERNAL FAILURE. REMOVED AND REPLACED THE START POWER UNIT, M1850 IAW B737-900 AMM 49-41-71. SPU INTALLATION TEST GOOD. STARTED APU 3 TIMES ON BATTERY.