Samsung Air Conditioner Error Code E309

E309 indicates a discharge temperature sensor error on fixed capacity compressor 2 in the outdoor unit. The system has detected a sensor signal voltage either above 4.95V (indicating an open circuit or temperature reading below -30 degrees Celsius) or below 0.5V (indicating a short circuit or temperature reading above 151 degrees Celsius). This fault is only detected when outdoor temperatures are above -10 degrees Celsius. The unit will not operate the affected compressor safely until the fault is resolved.

No. The discharge temperature sensor is a primary protection device for the compressor. Without a reliable reading from this sensor, the system cannot detect a compressor overheating condition, which can lead to compressor failure or refrigerant system damage. Samsung's control system raises E309 to halt operation of the affected compressor for this reason. Do not attempt to bypass the error or force the unit to run.

Repair costs depend on what has failed. If only the sensor connector needs reseating, costs are limited to a service call fee, typically in the range of $75 to $150. A replacement discharge temperature sensor for the outdoor unit generally costs between $20 and $80 for the part, plus labor. If the outdoor unit PCB needs replacement, total costs including parts and labor can range from $300 to $700 or more depending on the model and availability.

Some steps, such as checking whether the sensor connector has come loose and reseating it, can be done by a capable DIYer who is comfortable working in the outdoor unit with the power off. However, measuring sensor resistance accurately, tracing wiring faults, and replacing sensors or PCBs in a refrigerant system requires proper tools and in most regions a licensed technician. If basic connector inspection does not resolve the error, professional service is recommended.

A power reset may temporarily clear the error display, but if the underlying fault with the discharge sensor, its wiring, or its connector has not been corrected, the error will return once the unit resumes operation and the outdoor temperature is above -10 degrees Celsius. A reset is only useful as a final step after the sensor and wiring have been inspected and repaired.