What was found
AFTER LANDING, ATTEMPTED TWO APU STARTS. EACH ATTEMPT RECEIVED APU FAULT MESSAGE. REMOVED AND REPLACED APU DOOR ACTUATOR IAW AMM 49-15-06. NO FIX. UPON OPERATIONAL TEST FOUND CIRCUIT BREAKER TRIPPING. TROUBLESHOT IAW FIM 49-11 FT 959, REMOVED AND REPLACED THE K176 RELAY, PERFORMED APU OPS CHECKED IAW AMM 49-11-00. OPS CHECKED GOOD. NO DEFECTS NOTED.