LG Refrigerator Error Code UU/UU

The UU/UU error code on an LG refrigerator signals a simultaneous cooling failure in both the upper and lower compartments. Unlike single-zone faults, this code indicates the entire refrigeration circuit is compromised, producing a condition where both sections are experiencing either over-cooling or insufficient cooling at the same time. This dual-zone failure pattern points toward a central component in the sealed system or control circuit rather than an isolated evaporator or sensor issue. The overload protector (OLP) activation noted in this fault confirms the compressor or a related electrical component has tripped a safety device, cutting operation before damage can occur.

The switch valve, often a dual-function solenoid valve used in LG's linear or dual-evaporator systems, controls refrigerant flow direction between the fresh food and freezer circuits. If this valve fails to shift position correctly, refrigerant distribution becomes unbalanced across both zones simultaneously. A welding clog in the capillary tube is another high-probability cause: capillary tubes meter refrigerant flow, and any blockage from contamination or a manufacturing defect in a brazed joint will restrict or stop refrigerant movement entirely, starving both compartments. Improper coolant valve operation, whether from an electrical fault, a failed coil, or a stuck mechanical spool, produces the same full-system symptom pattern.

Diagnostic work should begin at the switch valve terminals, confirming correct voltage is being delivered and that the valve coil resistance is within specification. From there, a pressure test or temperature monitoring across the capillary tube inlet and outlet can reveal a restriction. If the OLP has tripped, identifying why the compressor overloaded, whether from refrigerant overcharge, a locked rotor, or high discharge pressure caused by a blockage, is essential before resetting or replacing any components.