LG Refrigerator Error Code F-defroster sensor short

The F-defroster sensor short error indicates a short circuit fault in the freezer area defrost sensor. This sensor is a thermistor that monitors temperature during the defrost cycle to prevent overheating of the evaporator and surrounding components. When the refrigerator's control board detects a reading that suggests the sensor output corresponds to a temperature above +50°C, it interprets this as an out-of-range condition consistent with a shorted thermistor rather than a legitimate temperature reading. A shorted sensor typically collapses its resistance to near zero, which the control board reads as an abnormally high temperature signal.

The freezer defrost sensor is positioned near the evaporator coils in the freezer compartment and works alongside the defrost heater and defrost thermostat to manage timed defrost cycles. When this sensor fails in a short condition, the control board loses accurate feedback about defrost cycle temperatures. This can cause the system to terminate defrost cycles prematurely or behave erratically, potentially leading to frost buildup on the evaporator over time.

The recommended first step is to run the refrigerator's self-diagnostic function to confirm the fault is active and isolated to this sensor. If the self-test confirms the F-defroster sensor short code, the sensor should be replaced. Before replacement, inspect the sensor wiring harness for pinched, chafed, or melted insulation that could create a short to ground independently of the sensor itself. If the wiring is intact, the sensor element is the most likely failed component.