Samsung Air Conditioner Error Code E405

E405 indicates that the COND-MID sensor on the outdoor unit has experienced a breakaway condition, meaning the condenser mid-point temperature sensor has become physically detached or displaced from its mounting position on the condenser coil. Without accurate mid-coil temperature data, the control board triggers this fault to prevent unsafe operation. Reseating the sensor is the recommended first step to resolve the error.

It is not recommended to continue operating the unit while E405 is active. The system is missing accurate mid-coil temperature data, which can lead to improper refrigerant management or compressor strain. Address the sensor displacement before resuming normal operation to avoid potential damage to the system.

A simple power reset is unlikely to permanently clear E405 if the underlying cause, a physically displaced sensor, has not been corrected. The error will return once the system restarts and detects the missing or inaccurate sensor signal. The sensor must be properly reseated and confirmed secure before the fault will stay cleared after a reset.

In many cases, a knowledgeable DIYer can resolve E405 by inspecting the outdoor unit and reseating the displaced COND-MID sensor into its retaining clip. Always disconnect power to the unit before accessing the outdoor unit panels. If the clip is broken or the wiring is damaged, a technician may be needed to source and install the correct replacement parts.

If only the sensor needs to be reseated, there may be no parts cost involved, and a technician's service call typically ranges from $75 to $150 depending on your area. If the retaining clip or the sensor itself needs replacement, parts costs can add $20 to $80 or more to the total. A full sensor and wiring harness replacement with labor could bring the total into the $100 to $250 range.