Samsung Air Conditioner Error Code 251

Error code 251 on a Samsung air conditioner indicates an open or short circuit fault in the digital compressor discharge temperature sensor. The control system detected a sensor voltage above 4.95 volts or below 0.4 volts, which falls outside the valid operating range. The error only activates when the outdoor temperature is above -10 degrees Celsius. The unit will not operate normally until the sensor circuit fault is resolved.

It is not advisable to continue running the unit with error code 251 active. The discharge temperature sensor exists to protect the compressor from overheating. Without accurate sensor data, the control system cannot detect a dangerous temperature condition, which could lead to compressor damage or failure. Addressing the fault before resuming normal operation is strongly recommended.

A power reset may temporarily clear the error code, but it will return if the underlying sensor circuit fault has not been repaired. The control system re-checks the sensor signal whenever the outdoor temperature is above -10 degrees Celsius and will re-trigger the fault if the voltage reading is still out of range. A reset is useful for confirming whether a repair was successful, but it is not a substitute for diagnosing and fixing the root cause.

A knowledgeable DIYer can start by inspecting the sensor wiring and connectors in the outdoor unit for obvious damage, corrosion, or loose connections, which are the most common causes. Reconnecting a loose connector or cleaning corroded terminals may clear the fault without any parts. However, replacing a failed sensor or outdoor PCB involves working inside the outdoor unit and handling refrigerant-side components, which is better suited for a certified HVAC technician.

If the fix is simply reseating a loose connector, there may be no parts cost, only a diagnostic service fee ranging from $75 to $150. Replacing a failed discharge temperature sensor typically costs between $50 and $150 for the part, plus labor. If the outdoor PCB requires replacement, total repair costs can range from $300 to $600 or more depending on the unit model and labor rates in your area.