Samsung Air Conditioner Error Code E425

E425 indicates a reverse phase or missing phase condition on the 3-phase power supply. The unit's phase detection circuit at connector CN82 has detected that the phase sequence is incorrect or that one or more of the three AC supply voltages (nominally 380V each) is absent. The system shuts down automatically to prevent damage to the compressor and motors.

A simple reset will not clear E425 if the underlying power supply problem still exists. The phase detection circuit monitors incoming power continuously, so the error will return immediately after restart if the phase sequence is still reversed or a phase is still missing. The root cause in the electrical supply must be corrected first before the unit will operate normally.

Repair costs vary depending on the root cause. If the issue is simply swapping two supply conductors for incorrect phase sequence, labor costs for a technician visit may range from $100 to $300. If a fuse, breaker, or contactor needs replacement, parts and labor could range from $150 to $600 or more. A main control board replacement, needed only if the phase detection circuit itself is faulty, is typically the most expensive repair and can range from $400 to over $1,000 including labor.

Diagnosing E425 involves working directly with 380V 3-phase power, which is dangerous and should only be handled by a qualified electrician or licensed HVAC technician. A technician will measure voltages at the CN82 connector across all three conductor pairs and check phase rotation. If the fix is simply swapping two supply conductors to correct phase sequence, a qualified professional can do this quickly, but it must not be attempted by an untrained person.

No. The unit will not run while displaying E425 because the shutdown is a protective measure. Attempting to force the unit to operate with reversed phase rotation would cause the compressor and fan motors to run in the wrong direction, leading to rapid mechanical failure. An open phase condition can also cause single-phasing, which overheats and destroys motor windings. The shutdown should be respected until the power supply issue is resolved.