What was found
AFTER SELECTING GEAR SELECT HANDLE TO THE GEAR DOWN POSITION, THE PILOT NOTED THE ACFT RECEIVED ALL 3 GREEN "DOWN AND LOCK" LIGHTS AND THE RED IN-TRANSIT "UNSAFE" LIGHT. OPERATOR DECLARED AN EMERGENCY LANDING AND LANDED WITHOUT INCIDENT. A POST FLIGHT INSP FOUND THE LT MAIN LANDING UP-LOCK SWITCH BAD BY TAPPING ON SWITCH WITH GEAR DOWN, COULD CAUSE THE RED UNSAFE LIGHT TO GO OUT. REPLACED LT MLG UP-LOCK SWITCH AND OPS CHECKED GOOD WHILE CYCLING GEAR SEVERAL TIMES.