Samsung Air Conditioner Error Code E311

E311 indicates a sump temperature digital sensor error on the outdoor unit. The control board has detected that the sensor signal voltage is either above 4.95V (open circuit, reading around -30°C) or below 0.5V (short circuit, reading around 151°C), both of which are outside the valid range. This fault is only triggered when the outdoor ambient temperature is above -10°C. It means the system cannot trust the sump temperature reading and has flagged a fault to protect the compressor.

Running the unit continuously with an active E311 error is not recommended. The sump temperature sensor protects the compressor from thermal damage, and without a valid signal, the system cannot adequately safeguard the compressor. Continued operation risks compressor damage, which is a costly repair. It is best to address the fault before resuming normal use.

A power reset may temporarily clear the E311 code, but the error will return if the underlying sensor fault still exists. Because the fault is triggered by a specific voltage threshold condition on the sensor circuit, the code will reappear once the unit restarts and the control board reads the out-of-range signal again. The physical cause, whether a loose connector, failed sensor, or damaged wire, must be corrected for the error to be permanently resolved.

A homeowner comfortable with basic electrical inspection can check whether the sensor connector has come loose from the outdoor PCB, which is the most common cause. However, testing sensor resistance, inspecting wiring for damage, and replacing components on the outdoor unit PCB requires proper tools and electrical knowledge. If the sensor or board needs replacement, a qualified HVAC technician should handle the repair.

Repair costs depend on the root cause. If the fix is simply reseating a disconnected connector, there may be minimal to no parts cost, with only a service call fee typically ranging from $75 to $150. A replacement sump thermistor sensor generally costs between $20 and $80 for the part itself. If the outdoor PCB needs replacement, total costs including parts and labor can range from $300 to $700 or more depending on the unit model.