Samsung Air Conditioner Error Code 428

Error code 428 means the compressor has been shut down by the system's compression ratio protection logic. The ratio of (high-side pressure + 1) divided by (low-side pressure + 1) exceeded 8.5 and stayed above that level for more than 10 minutes. This indicates an abnormal pressure condition in the refrigerant circuit, most often caused by a refrigerant shortage, a flow restriction, or an expansion valve problem. The compressor is disabled to prevent mechanical damage.

No. The system has already shut the compressor down as a protective response, and attempting to force the unit to continue operating under these conditions risks serious compressor damage. Leave the unit off and contact a technician promptly. Running the system with an abnormal compression ratio can cause refrigerant flooding, overheating, or compressor failure, all of which are significantly more expensive to repair than the underlying cause of the error.

Repair costs vary widely depending on the cause. A simple service valve adjustment or refrigerant recharge typically runs between $150 and $400 including the diagnostic visit. If an indoor or outdoor EEV needs replacement, costs generally range from $300 to $700 or more depending on parts availability and labor rates. A full refrigerant leak repair with recharge can add to those figures. Getting a diagnostic from a certified technician is the best way to obtain an accurate estimate for your specific situation.

Most of the repairs associated with error 428 require EPA 608 certification to handle refrigerant legally, so a licensed HVAC technician is needed for anything involving the refrigerant circuit. A homeowner can check that the outdoor unit is unobstructed and that any accessible service valves appear fully open, but diagnosing pressure ratios, testing EEV operation, and adding refrigerant must be performed by a qualified technician with manifold gauges and S-net diagnostic tools.

A power reset may temporarily clear the error and allow the compressor to restart, but the fault will return if the underlying pressure issue is not resolved. Because the shutdown requires the ratio to exceed 8.5 for more than 10 continuous minutes, the root cause such as low refrigerant, a closed valve, or a failed EEV will reproduce the same condition during the next operating cycle. A reset is useful during diagnosis to observe system behavior, but it is not a fix.