Samsung Air Conditioner Error Code 31

Error code 31 on a Samsung air conditioner indicates a discharge temperature sensor fault on the outdoor unit. The outdoor control board has detected either an open circuit or a short circuit in the sensor connected at PIN#3 and PIN#4 of connector CN51. This sensor monitors refrigerant temperature leaving the compressor, and without a valid reading, the system limits or stops operation to protect the compressor.

It is not recommended to continue operating the unit with error code 31 active. The discharge temperature sensor is a key compressor protection input, and without a valid reading the control system cannot properly guard against overheating. Running the system in this condition risks compressor damage, which is significantly more expensive to repair than the sensor itself.

A power reset may temporarily clear the error code display, but the fault will return as soon as the outdoor control board re-reads the sensor signal at CN51 and detects the open or short circuit again. Because the underlying cause is a hardware fault in the sensor or wiring rather than a software glitch, clearing the code without repairing the sensor circuit will not restore normal operation.

Some basic checks are accessible to a knowledgeable DIYer, such as inspecting the wiring harness for visible damage and reseating the connector at CN51 on the outdoor control board. However, accurately diagnosing an open or short circuit in the sensor requires a multimeter and familiarity with reading thermistor resistance values. Replacing the sensor or the outdoor control board is best handled by a qualified technician, especially since working inside the outdoor unit involves electrical components.

Repair costs vary depending on the root cause. A replacement discharge temperature sensor typically falls in the range of $15 to $60 for the part alone, while labor charges for an HVAC technician can add $75 to $200 depending on your region and the complexity of access. If the fault turns out to be a failed outdoor control board, part costs can range from $150 to $400 or more, making a proper diagnosis before ordering parts especially important.