What was found
ELECTRICAL FAULT CYAN CAS: CYAN ELECTRICAL FAULT EICAS MSG CAME ON DURING THE CLIMB PASSING FL200. THE BUS TIE SWITCH CLOSED. THE LEFT AUX BUS WAS ISOLATED. THE LEFT MAIN BUS WAS FED BY THE LEFT GEN. THE L ESS BUS WAS FED BY THE RIGHT GEN VIA THE BUS TIE. THE L AUX BUS RECONNECTED TO THE L MAIN BUS DESCENDING THROUGH FL200. THE B3 CODE IN THE AIR WHILE THIS WAS GOING ON WAS:B3-007122, LEFT PROTECTION PCB (LPROT) FAILURE. CHECK THE LEFT PROTECTION PCB PCB1 IN THE LDCPC (A35). THE MESSAGE TURNED AMBER UPON LANDING. CORRECTIVE ACTION; SWAPPED LT & RT ENGINE GENERATORS FOR CUSTOMER CONVENIENCE. RAN BOTH ENGINES AND PERFORMED MAIN GENERATOR OPERATIONAL TESTS WITH NO DEFECTS NOTED. REF. CL350 AMM 24-31-05.