Whirlpool 4387490 Bimetal Thermostat for Refrigerator Defrost (IT18DKXSQ00, 4387490, PS371245, AP3108445) Defrost thermostat for Whirlpool 4387490 Refrigerator. New and High quality ensured. Hi-Limit. Genuine Replacement Part It is used on Hotpoint and other refrigerator brands listed below.