What was found
TWO UNSUCCESSFUL STARTS OF THE APU, RECEIVED AMBER FAULT LIGHT ON BOTH TRIES. (ALSO NO RISE IN EGT). GROUNDED - YES. PER TROUBLE SHOOTING NOTES. REPLACED START POWER UNIT, START CONVERTER UNIT, ELECTRONIC CONTROL UNIT. OPENED/TAGGED 2CBS. RMVD AND INSTALLED ECU. RMVD TAGS/CLOSED 2CBS. DUE TO MESSAGE 45-15004 INLET DOOR SHUT DOWN. REF 49-61-12/401. OPENED /TAGGED 3CBS. RMVD AND INSTALLED NEW SC UNIT . RMVD TAGS/CLOSED 3CBS. REF 49-41-61/401 OPENED /TAG 4CBS. RMVD AND INSTALLED NEW START POWER UNIT. RMVD TAGS/CLOSED 4CBS REF 49-41-71/401. PERFORMED GROUND OPS VERIFICATION AND RAN / STARTED APU 2X. NO FAULTS NOTED. CLEAR MEL 49-1B. REF LO 60070745 FOR APPLICATION OF MEL 49-99A. SEAMC MARK NOTIFIED.