Samsung Air Conditioner Error Code P420

P420 is a high pressure protection code that activates when the high pressure sensor detects refrigerant pressure exceeding 28 kg/cm²G on the discharge side of the system. The unit shuts down automatically to prevent compressor and component damage. The fault must be diagnosed and corrected before the system will operate normally again.

No. The P420 code represents a high pressure condition that can damage the compressor and other refrigerant circuit components if ignored. The unit shuts down as a safety measure, and attempting to override or bypass this protection is not recommended. Address the root cause before resuming operation.

Repair costs vary significantly depending on the cause. Cleaning a condenser coil or opening a service valve is relatively low cost, typically in the range of $75 to $200 for a service call. Replacing a PWM expansion valve coil or a high pressure sensor can range from $150 to $500 or more depending on parts and labor. Refrigerant-related repairs may add to the total if recovery and recharge are required.

Some causes, such as a closed service valve or a dirty condenser coil, can be addressed without specialized tools. However, diagnosing the PWM valve coil, checking refrigerant charge, or replacing the high pressure sensor requires refrigerant handling equipment and electrical testing skills. If you are not experienced with HVAC systems, a certified technician should handle this repair.

A power reset may temporarily clear the displayed code, but if the underlying cause of high pressure is still present, the P420 error will return as soon as the system attempts to operate again. Resetting without resolving the fault can also allow repeated high-pressure events that accelerate wear on the compressor. The cause must be corrected first.