LG Refrigerator Error Code R0 ON, R1-R4 OFF

This code indicates that the defrost sensor has been detected as either shorted or open by the control board. The defrost sensor is a thermistor that monitors evaporator coil temperature during the defrost cycle. When the sensor or its wiring circuit fails, the control board logs this fault and the refrigerator cannot properly regulate the defrost heater. The result is typically a loss of defrost cycle control, which can lead to ice accumulation on the evaporator coils.

A power reset may temporarily clear the error code from the display, but it will return if the underlying defrost sensor or wiring fault has not been corrected. The control board will re-detect the open or short circuit as soon as it attempts to monitor the defrost cycle. A lasting repair requires diagnosing and fixing the faulty sensor or wiring.

If only the defrost sensor thermistor needs to be replaced, parts typically cost in the range of $15 to $50 depending on the specific model. If professional labor is required, the total repair cost including parts and service can range from $100 to $250. Wiring harness repairs or connector replacements may add to this cost depending on the extent of the damage.

Start by checking the defrost sensor's resistance with a multimeter to determine whether it is open or shorted. Also inspect the wiring harness and connector terminals for damage, corrosion, or loose pins. If the sensor itself has failed, it will need to be replaced. If the wiring is damaged, the affected section of the harness or the connector will need to be repaired or replaced.

The refrigerator may continue to run for a period of time, but without a functioning defrost sensor, the defrost cycle cannot be properly controlled. This can lead to progressive ice buildup on the evaporator coils, which reduces airflow and cooling efficiency throughout the unit. Continued operation in this state risks food spoilage and potential damage to other components, so the fault should be addressed promptly.