Samsung Air Conditioner Error Code P423

Error code P423 on a Samsung air conditioner indicates a self-diagnosis failure for the outdoor unit's Electronic Expansion Valve (EEV) close position 2. The EEV is a precision refrigerant flow control component that regulates the amount of refrigerant entering the indoor coil by adjusting its opening based on signals from the main control board. The "close 2" designation refers to a specific closing position test conducted during the self-diagnosis routine, where the system verifies that the valve can fully seat and hold the closed position correctly. When this test fails, the system generates P423 to alert technicians to a fault in EEV operation.

The self-diagnosis routine runs the EEV through a series of commanded positions and monitors feedback to confirm proper valve response. A failure at the close 2 stage typically points to a mechanical binding issue within the valve body, a stepping motor that has lost synchronization or has failed internally, or a wiring fault between the valve and the outdoor unit control board. In some cases, contaminated refrigerant or debris within the refrigerant circuit can obstruct the valve needle, preventing full closure.

Because the EEV directly controls refrigerant flow, a fault in this component can cause improper system pressures, reduced cooling or heating capacity, and potential compressor damage if left unaddressed. Diagnosis should involve inspecting the EEV wiring harness for continuity and damage, checking the coil resistance of the stepping motor against specifications, and confirming that the control board is delivering the correct pulse signals to the valve driver circuit.