Samsung Air Conditioner Error Code 257

Samsung air conditioner error code 257 indicates a fault in the discharge temperature sensor circuit for fixed scroll compressor 2. This sensor monitors the temperature at the discharge port of the second fixed scroll compressor, which is a critical measurement point for protecting the compressor from overheating during operation. The system detects this fault when the sensor signal voltage rises above 4.95V, corresponding to a temperature reading of approximately -30 degrees Celsius, or drops below 0.5V, corresponding to approximately 151 degrees Celsius. These voltage thresholds represent open-circuit and short-circuit conditions respectively, meaning the sensor or its wiring has lost signal integrity rather than simply reading an out-of-range temperature.

The discharge temperature sensor is a thermistor-based component whose resistance changes predictably with temperature. When the circuit is open, resistance becomes effectively infinite and the control board reads an abnormally high voltage. When the circuit is shorted, resistance collapses and voltage drops toward zero. Both conditions trigger error 257 because neither represents a valid operating temperature for a running compressor. This type of fault prevents the system from protecting the compressor against thermal overload, so the unit will typically shut down or restrict operation as a safety measure.

The first diagnostic step is to physically inspect the wiring and connector associated with the fixed scroll compressor 2 discharge temperature sensor. This includes checking for broken wires, corroded or unseated connector pins, and damaged connector housings at both the sensor end and the PCB connection point. Wiring routed near hot components or moving parts is particularly susceptible to chafing and insulation breakdown over time.