What was found
FLT 198 - MLM-TIJ - AIRCRAFT RETURNED TO GATE, FAIL LIGHT AC/CROSSTIE LOCK-OUT OFF RESET PROCEDURE WS PERFORMED AND LIGHT WAS TURN OFF, BUT LIGHT L GEN OFF APPEARS. GCU WAS NOT POSSIBLE RESET AND ENGINES WERE SHUTDOWN. REPORT WAS DEFERRED UNDER MEL 24-1-1 AND AIRCRAFT WAS REFUELED. DURING OVERNIGHT SERVICE, GENERATOR (P/N 976J252-8) AND GCU WERE CHANGED IAW MM 24-20-01, ALL CORRECT. (M)