LG Refrigerator Error Code F-DEF-SEN

F-DEF-SEN means the refrigerator's self-diagnostic system has detected a failure in the freezer defrost sensor circuit. The defrost sensor is a thermistor that monitors evaporator temperature during the defrost cycle and signals the control board when defrost should stop. The error is confirmed by checking resistance at connector CN30 between pins No.4 and No.7, where a reading of 0 ohms indicates a short and a reading of infinity indicates an open circuit.

Continued use is not recommended for an extended period. Without a functioning defrost sensor, the refrigerator cannot properly control the defrost cycle, which can lead to ice buildup on the evaporator coil and gradual loss of cooling performance in both the freezer and fresh food compartments. Food safety may be at risk if temperatures rise beyond safe storage levels.

A power reset may temporarily clear the error code from the display, but the code will return if the underlying sensor or wiring fault is not repaired. Because this error is generated by the refrigerator's self-diagnostic system detecting a measurable circuit fault, the root cause must be corrected before the error will clear permanently.

A knowledgeable DIYer with a multimeter can diagnose this code by testing resistance at CN30 pins No.4 and No.7 after unplugging the refrigerator. If the wiring harness shows visible damage or the connector is corroded, those repairs are relatively straightforward. Replacing the defrost sensor thermistor is also a common DIY repair, but if the control board is determined to be at fault, professional service is recommended.

If only the defrost sensor thermistor needs replacement, parts typically range from around 15 to 50 dollars depending on the specific model. Professional labor to diagnose and replace the sensor generally adds 100 to 200 dollars. If the control board is the cause, parts and labor costs can range from 200 to 500 dollars or more.