LG Refrigerator Error Code R4 R5

The R4 and R5 error codes on LG refrigerators indicate a defrost system malfunction. Specifically, the control board triggers this fault when the defrost sensor fails to register a temperature above 50°F (10°C) within 2 hours of the defrost cycle beginning. This means the evaporator coils are not being adequately heated during the defrost cycle, which will lead to progressive ice buildup on the evaporator and eventually a loss of cooling performance throughout the refrigerator and freezer compartments.

The defrost system relies on several components working together: a defrost heater that melts accumulated ice on the evaporator coils, a thermal fuse that cuts power to the heater if temperatures become unsafe, a defrost sensor that monitors temperature progress, and a relay that controls heater activation. If any one of these components fails, the sensor will not reach the required threshold and the R4 or R5 code will be triggered. A clogged drain can also contribute to the problem by causing ice to accumulate at the drain pan and interfere with proper heat distribution during the cycle.

Diagnosis should begin with a visual inspection of the evaporator compartment for excessive ice buildup, followed by continuity testing of the thermal fuse and defrost heater. The thermal fuse, when blown, will show no continuity and must be replaced. The heater should also show continuity when cold. If both components test good, inspect the defrost relay on the control board and verify the drain path is clear of ice or debris.