What was found
DURING APPROACH INTO YEG, THE LEFT MAIN LANDING GEAR RED UNSAFE LIGHT REMAINED ON AFTER GEAR WAS EXTENDED. GO-AROUND PROCEDURES WERE EXECUTED AND CREW REQUESTED EMERGENCY EQUIPMENT ON STANDBY AS A PRECAUTION. GEAR WAS VISUALLY CONFIRMED THROUGH PERISCOPE TO BE DOWN AND LOCKED. AN UNEVENTFUL LANDING WAS ACCOMPLISHED. MAINTENANCE FOUND MOISTURE AND SLIGHT PIN CORROSION ON LEFT MAIN GEAR DOWNLOCK SWITCH. CLEANED SWITCH, OPERATIONAL CHECK NORMAL ON SYSTEM CHECK.