LG Refrigerator Error Code R3 R4 R5 ON

This code indicates the refrigerator's automatic defrost cycle ran for more than one hour without the defrost sensor reaching 50°F (10°C). It points to a failure in the defrost system, which can involve the thermal fuse, defrost heater, defrost sensor, heater drive relay, or a blocked drain. The refrigerator detected that frost was not being cleared properly and flagged the fault to prevent ongoing cooling problems.

Start by checking the thermal fuse (FUSE-M) for continuity, since a blown fuse is a common cause. Also test the defrost sensor resistance, inspect the heater drive relay, and examine the defrost drain for ice or debris blockage. If the defrost heater itself has an open circuit, it will need to be replaced. Each component should be tested individually to pinpoint the failure before replacing parts.

Repair costs depend on which component has failed. Replacing a thermal fuse or defrost sensor is generally on the lower end, typically in the range of $50 to $150 including parts and labor. A defrost heater or control board relay repair may run $100 to $300 or more depending on parts pricing and technician rates in your area. Getting a diagnosis first helps avoid replacing parts unnecessarily.

A reset may temporarily clear the displayed code, but it will not fix the underlying defrost system failure. If the root cause is not repaired, the refrigerator will attempt another defrost cycle, fail again, and the code will return. It is important to diagnose and correct the faulty component before relying on a reset.

Continued use is not recommended without addressing the problem. Without a functioning defrost cycle, frost will progressively build up on the evaporator coil, restricting airflow and reducing the refrigerator's ability to maintain safe food storage temperatures. Over time, this can lead to spoiled food and additional component stress.