What was found
DURING FLIGHT 577 TO KEF, LEFT MAIN GEAR GREEN DOWN LIGHT NOT ON AND GEAR UNSAFE LIGHT ILLUMINATED, RECYCLED GEAR WITH SAME RESULT. PERFORMED CHECK PER QRH AND DETERMINED GEARS WERE DOWN AND LOCKED, AIRCRAFT LANDED WITHOUT INCIDENT. INSPECTED LT GEAR DOWNLOCK SWITCH, FOUND ICE BUILD-UP ON SWITCH, CLEANED AND OPS CHECKED GOOD PER M.M. CH 32.