What was found
DURING TAXI TO GATE, STARTED APU. THE APU STARTED BUT NO APU GEN OFF BUS LIGHT ILLUMINATED AND APU GEN VOLTMETER SHOWED ZERO VOLTS. APU GEN INOP. GROUNDED - YES. PERFORMED NORMAL OPERATION OF APU MULTIPLE TIMES PER B737-900 AMM 49-11-00. VOLTAGE AND FREQS WERE NORMAL NO DISCREPANCIES NOTED. PERFORMED APU BITE PER FIM 49-60 TASK 801. FOUND 2 FAULTS. FAULT 1 MESSAGE 49-41255. START POWER UNIT SHOWS HIGH TEMP. REMOVED AND REPLACED START POWER UNIT PER AMM 49-41-71. PERFORMED GOOD OPS TEST OF START POWER UNIT PER AMM 49-41-71-400-801. PERFORMED BITE TEST OF APU PER AMM 49-61-00 AND FAULT MESSAGE CLEARED.