What was found
LEFT MAIN DOWN AND LOCK INDICATION DID NOT COME ON WHEN GEAR WAS EXTENDED. NO RED LIGHT ON. ABNORMAL PROCEDURE ACCOMPLISHED. (FLY BY FOR MAINTENANCE TO VERIFY GEAR DOWN.) AFTER SITTING STOPPED ON RUNWAY FOR FIVE MINUTES THE LEFT MAIN GEAR GREEN LIGHTS CAME ON. FOUND LEFT HAND MAIN LANDING GEAR DOWNLOCK SWITCH PINS CORRODED. REPLACED SWITCH, OPS CHECKED GOOD IAW DC8 SMM 32-10-00.