What was found
DURING LEFT ENGINE STARTING, CAPTAIN REPORTED DFGC NR 1 OUT OF SERVICE AND FLIGHT DIRECTOR SHOWED FD AND SPD MESSAGES. ENGINES WERE SHUTDOWN. DFGCS WERE INTERCHANGED AND BREAKERS WERE RESET, DISAPPEARING TRI FLIGHT DIRECTOR FLAGS. TESTS WERE PERFORMED IAW MM 34-22-00. DURING OVERNIGHT SERVICE, RETURN TO SERVICE TEST TO BOTH DFGCS WERE PERFORMED IAW MM 22-01-05, TESTED CORRECT.