UPDATE 1-Visteon agrees to sell S.Korean unit for $3.6 bln

SEOUL, Dec 18 (Reuters) - U.S. auto parts maker Visteon Corp has agreed to sell its majority-owned South Korean unit for $3.6 billion, cashing in on a quadrupling of the air conditioning firm's share price in the last five years as Visteon refocuses on in-car electronics.