Samsung Air Conditioner Error Code E423

E423 indicates an open or short circuit fault on the SUMP TEMP FIXED 3 sensor in the outdoor unit. The error triggers when the sensor voltage rises above 4.95V or drops below 0.5V, placing it outside the valid measurement range. This sensor monitors sump temperature and is only active when outdoor temperatures are above -10°C. The fault can be caused by a failed sensor, a damaged connector, or a wiring harness issue.

Continuing to operate the unit with an active E423 fault is not advisable. The sump temperature sensor helps protect the compressor and manage refrigerant behavior. Running the system without a valid sensor reading can lead to compressor damage or reduced efficiency. It is best to resolve the fault before resuming normal operation.

A power reset may temporarily clear the error code from the display, but the fault will return if the underlying hardware problem is not corrected. The control board will detect the out-of-range sensor signal again once the unit restarts and outdoor temperatures are above -10°C. A permanent fix requires identifying and repairing or replacing the defective component.

A knowledgeable DIYer can perform the initial diagnostic steps, including inspecting the sensor connector and measuring resistance across the sensor terminals with a multimeter. If the sensor reads open or short, replacing the thermistor is a relatively straightforward task. However, if the fault traces back to the control board, professional service is recommended.

If only the sensor needs replacement, repair costs typically fall in the range of $75 to $200, depending on labor rates and part availability. If the control board is the root cause, costs can rise to the range of $250 to $600 or more. Getting a diagnosis first will help narrow down the scope of the repair.