What was found
(CAN) AFTER THE LANDING GEAR WAS SELECTED DOWN, THE CREW REPORTED THE LEFT MAIN GEAR GREEN LIGHT DID NOT ILLUMINATE. WHILE CIRCLING FOR A VISUAL INSPECTION, THE LIGHT CAME ON. AFTER LANDING THE MAINTENANCE CREW CLEANED AND LUBRRICATED THE SWITCH AND PERFORMED FUNCTIONAL CHECKS. THE LANDING GEAR OPERATED NORMALLY. THE SUBMITTER STATES THAT SERVICE BULLETIN 32-JA- 891142 ADDRESSESTHE ISSUE OF MOISTURE CONTAMINATED SWITCHES BY REPLACEMENT WITH AN IMPROVED UNIT.