Samsung Air Conditioner Error Code 431

Samsung air conditioner error code 431 relates to a self-diagnosis failure in Balance Keeping Valve 1, which is the oil valve in the refrigerant circuit. This valve is responsible for maintaining proper oil distribution across the system, a critical function in multi-split and VRF (Variable Refrigerant Flow) configurations where compressor oil must be balanced between multiple units. The error triggers when the system detects either an open-circuit or closed-circuit failure in the valve mechanism, or when the associated temperature sensor reports an out-of-range or implausible reading indicating sensor displacement or defect.

The fault has two primary aspects: a mechanical or electrical valve failure, and a sensor-related failure. On the valve side, the system checks whether the oil service valve is physically open and whether the valve coil and connector are properly seated and energized. A disconnected, corroded, or failed coil will prevent the valve from operating through its normal range, triggering the self-diagnosis fault. On the sensor side, the oil valve temperature sensor 1 must be correctly positioned and making proper thermal contact. If this sensor has shifted out of position, become damaged, or developed an open or short circuit in its wiring, the control board cannot confirm valve operation and logs code 431.

Diagnosis should begin by physically inspecting the oil valve temperature sensor 1 for displacement or visible damage, then confirming the oil service valve is in the fully open position. The valve connector and coil should be checked for secure seating, continuity, and any sign of burning or corrosion. If the sensor and wiring check out but the fault persists, the valve coil or the valve body itself may require replacement.