LG Refrigerator Error Code R4

The R4 code means the defrost sensor did not reach 50°F (10°C) within one hour after the defrost cycle started. The control board uses this threshold to confirm a successful defrost. Because the compressor, freezer motor, and defrost heater are all confirmed operational when this code appears, the fault points specifically to the defrost sensor or its wiring circuit.

The R4 error is not an immediate safety hazard. It does not indicate an electrical short, refrigerant leak, or fire risk. However, if left unresolved, the defrost cycle will continue to fail, leading to progressive ice accumulation on the evaporator coil. Over time this can reduce cooling efficiency, restrict airflow, and potentially cause food spoilage.

A power reset may temporarily clear the R4 code from the display, but it will not resolve the underlying fault. If the defrost sensor or its circuit has not been repaired, the code will return the next time the refrigerator attempts a defrost cycle and the sensor again fails to reach 50°F within one hour. A permanent fix requires diagnosing and correcting the sensor or wiring issue.

Some causes of R4 are DIY-accessible, such as checking for ice buildup around the sensor, verifying the sensor is properly clipped onto the evaporator coil, and inspecting the wiring harness for loose connectors. Measuring sensor resistance with a multimeter requires basic technical skill but is within reach for a knowledgeable homeowner. Replacing the control board or sensor wiring harness is more involved and may warrant a professional technician.

Repair costs vary depending on the root cause. A replacement defrost sensor typically costs between $15 and $50 for the part, while a main control board can range from $100 to $250 or more. If you hire a technician, expect to add $75 to $150 or more in labor costs depending on your location and the complexity of the repair.