What was found
SEA - ON ARRIVAL OF FLT 451 CREW REPORTED, DURING APPROACH WHEN THE LANDING GEAR WAS EXTENDED, THE GEAR WARNING HORN SOUNDED AND ALL THREE GEAR UNSAFE LIGHTS ON. CYCLED LANDING GEAR, APPROXIMATELY 15 SECONDS AFTER GEAR EXTENDED THE SECOND TIME, THE WARNING HORN SILENCED AND ALL GEAR POSITION LIGHTS INDICATED DOWN AND LOCKED. REPLACED THE LANDING GEAR HANDLE SWITCH AND THE LEFT THROTTLE SWITCH ASSEMBLY. ACCOMPLISHED GEAR SWING AND OPERATED NORMALLY. REFERENCE ASAA9580136.