What was found
APU FAULT LIGHT ON FIRST START ATTEMPT ON TAXI IN, WAITED 5 MINUTES, FAULT CLEARED, SUCCESSFUL START ON ATTEMPT #2. GROUNDED - YES. PERFORMED TROUBLESHOOTING & FOUND MAINTENANCE MESSAGE 49-41012 NO APU ROTATION SHUTDOWN & 49-41254 START CONVERTER UNIT SHOWS START SYSTEM INOP. PERFORMED B737-9 IFIM TASK 49-40-00-810-805 STEPS 1 & 2. MESSAGES SHOW AS NOT ACTIVE & NO PREVIOUS HISTORY ON A/C. COMPLETED APU START WITH NO FAULTS NOTED NOTED. FAULTS ARE INTERMITTENT.