Samsung Air Conditioner Error Code 151

Error code 151 on a Samsung air conditioner signals a second opening failure of the indoor electronically controlled expansion valve, commonly referred to as the EEV (Electrically Operated Valve). The EEV is a precision refrigerant metering component that regulates refrigerant flow into the indoor heat exchanger by opening and closing in response to control signals from the PCB. A "second opening error" indicates that the system attempted to open the valve a second time and the valve either did not respond, did not reach its target position, or reported back an unexpected condition. This distinguishes it from a first opening fault and typically points to a persistent mechanical or electrical failure rather than a transient issue.

The EEV coil is the electromagnetic component responsible for actuating the valve. When the coil develops an internal breakage, a short circuit, or suffers corrosion due to external rust, it loses the ability to produce the magnetic force required to drive the valve needle to its open position. Connection integrity at the PCB header is equally critical: a loose, corroded, or damaged wire harness between the EEV and the indoor PCB will interrupt the drive signal, producing the same fault symptom without any issue in the valve body itself. Sealing condition around the valve assembly also matters, since moisture intrusion can accelerate coil degradation and cause erratic valve behavior.

Diagnosis should begin at the PCB-side connector for the EEV wire harness, verifying secure seating and checking for pin corrosion or damage. The coil should be inspected visually for rust and tested for resistance and continuity to confirm there is no open circuit or short. After addressing any wiring or coil issues, resetting the outdoor unit (K3) and rechecking operation is the recommended final step to confirm whether the fault clears under normal operating conditions.