What was found
ON INITIAL CLIMB DURING LANDING GEAR RETRACTION WE OBSERVED THE FOLLOWING. FOR ABOUT 15 SECONDS THE LT MAIN GEAR UNSAFE LIGHT, LT DOOR ADV LIGHT, AND THE GEAR HANDLE LIGHT REMAINED ILLUM. THEN AFTER 15 SECONDS THE GEAR FINISHED RETRACTION NORMALLY, BOTH ALTERNATE EXTENSION DOORS WERE CLOSED NORMAL (WE DIDN'T HAVE TIME TO RUN GEAR FAILS TO RETRACT CHECKLIST BEFORE GEAR FIXED ITSELF). GEAR EXT WAS NORMAL. REMOVED FROM SERVICE. INTERROGATED PSEU FOR FAULTS, NO CURRENT FAULTS. PERFORMED GVI OF MLG, NO OBVIOUS DEFECTS. FERRIED AIRCRAFT. REPLACEMENT OF LT MLG SOLENOID SEQ VALVE AND FLUSHING OF LT MLG DOOR ACTUATOR LINES DUE TO FINDINGS DURING TROUBLESHOOTING. LANDING GEAR PRIMARY EXT AND RET SYSTEM OPERATIONAL TEST GOOD SEVERAL TIMES AT BOTH LOW AND NORMAL FLOW SETTINGS, IAW DHC-8-400 MM TASK NR 32-31-00-710-801. LANDING GEAR PRIMARY EXT AND RET SYSTEM FUNCTIONAL TEST GOOD, IAW DHC-8-400 MM TASK NR 32-31-00-720-801. AIRCRAFT RETURNED TO SERVICE.