What was found
BOS - FLT 4390 - WHEN GEAR SELECTED DOWN FOR LANDING, THE NOSE GEAR GREEN DOWN AND LOCK LIGHT ILLUMINATED THEN EXTINGUISHED. CREW CYCLED GEAR AND ALL INDICATIONS WERE NORMAL. AIRCRAFT LANDED WITHOUT INCIDENT. MAINTENANCE CLEANED AND LUBRICATED NOSE DOWN LOCK SWITCH AND CLEANED ELECTRICAL CONNECTORS GOING TO SWITCH. SYSTEM TESTED NORMAL, AIRCRAFT WAS RETURNED TO SERVICE. (M)