Samsung Air Conditioner Error Code E424

Error code E424 on a Samsung air conditioner indicates a fault detected in the high pressure sensor circuit. The high pressure sensor monitors refrigerant pressure on the discharge side of the compressor, and the control board evaluates the sensor's output voltage to determine circuit status. A SHORT condition is flagged when the sensor voltage drops below 0.4V, while an OPEN condition is flagged when the voltage rises above 4.2V. Both fault states are detected specifically when the compressor is preparing to operate, meaning the unit has determined a reliable reading should be available at that moment.

The high pressure sensor is a critical safety component. It prevents the compressor from operating under dangerously high refrigerant pressures, which could cause compressor damage or refrigerant line failure. When the control board reads a voltage outside the 0.4V to 4.2V operating window, it interprets the signal as an invalid reading and locks out compressor operation to protect the system. This voltage range corresponds to the sensor's normal analog output across the expected pressure spectrum.

Importantly, E424 detection is intentionally skipped during oil collection mode, safety start sequences, and defrost cycles. These operational modes involve atypical refrigerant flow and pressure conditions that could produce misleading sensor readings. Diagnostics should not be performed during these phases. Wait at least 5 minutes after any of these cycles complete before evaluating the sensor circuit or attempting to interpret live voltage readings from the sensor connector.