Samsung Air Conditioner Error Code P428

P428 indicates that the compression ratio on outdoor unit compressor 1 has exceeded 8.5 and held that level for 5 consecutive minutes. This ratio is calculated from discharge pressure versus suction pressure, and a reading this high means the compressor is under abnormal stress. The error is designed to protect the compressor from damage caused by sustained operation outside safe pressure limits.

Continuing to operate the unit with P428 active is not advisable. A sustained compression ratio above 8.5 places extreme mechanical and thermal stress on the compressor. Prolonged operation in this state can cause permanent compressor failure, which is a significantly more expensive repair than addressing the underlying cause early.

Repair costs depend heavily on the root cause. Correcting a closed service valve or cleaning a blocked coil is relatively inexpensive, typically in the range of $75 to $200 for a service call. Replacing a PWM valve coil or recharging refrigerant after a leak repair can run $200 to $600 or more. If the compressor has already sustained damage, replacement costs can range from $800 to well over $2,000 depending on the unit.

One check a homeowner can safely perform is confirming that the outdoor unit is not blocked by debris and has adequate airflow clearance. However, most of the root causes, including checking service valves, testing the PWM valve coil, and verifying refrigerant charge, require technical knowledge and, in the case of refrigerant handling, EPA certification. It is strongly recommended to have a qualified HVAC technician complete the diagnosis and repair.

A power reset may temporarily clear the fault code, but if the underlying condition, such as a closed service valve, a faulty PWM valve, or low refrigerant, has not been corrected, the error will return once the compression ratio exceeds 8.5 again for 5 minutes. Resetting without diagnosis and repair is not a solution and risks compressor damage.