LG Refrigerator Error Code FCT0

The FCT0 error code on an LG refrigerator indicates a compressor PCB parts defect, specifically classified as a piston overaction condition. This fault is triggered when the compressor control board detects an anomaly during its self-check routine involving motor voltage and current sensing. The inverter compressor system continuously monitors electrical parameters to ensure the compressor is operating within safe limits. When the sensed values fall outside acceptable thresholds, the board registers this as a sensing error and logs the FCT0 code.

The compressor PCB, also called the inverter control board, is responsible for regulating the variable-speed compressor motor. It converts incoming AC power to DC, then produces a controlled AC output to drive the compressor at varying speeds depending on cooling demand. A defect in the sensing circuitry, whether in the current transformers, voltage divider components, or onboard microprocessor, can cause the board to misread motor behavior and interpret normal operation as piston overaction.

The first recommended diagnostic step is a power reset, which allows the board to reinitialize and clear any transient fault conditions. If the FCT0 code returns after the reset, the compressor PCB itself is the confirmed failure point and must be replaced. In some cases, a loose or corroded connection at the board harness can produce intermittent sensing errors, so inspecting all connectors at the compressor board before ordering parts is a worthwhile step.