What was found
LEFT FMC FAILED FOUR TIMES ENROUTE THEN RETURNED TO NORMAL OPS. THE LAST FAILURE LEFT FMC WOULD NOT RETURN TO NORMAL, REFERENCED QRH 11.3 FMC FAIL. ACFT GROUNDED. ACCOMPLISHED LEFT FMC BITE IAW FIM 34-61 TASK 801. FOUND FMC L-PGM FAULT LOGGED 2 TIMES. PERFORMED FIM 34-61 TASK 807. NO CURRENT FAULT FOUND BUT DUE TO PREVIOUS WRITE-UPS REPLACED LEFT FMC. REMOVED & INSTALLED NEW LEFT FMC COMPUTER, IAW AMM 34-61-00. ACCOMPLISHED SOFTWARE CROSSLOAD IAW AMM 34-61-00/201. ACCOMPLISHED FACTORS ADJUSTMENT, IAW AMM 34-61-00. ACCOMPLISHED FMC OPS TEST, IAW AMM 34-61-00. SYSTEM CHECKED NORMAL.