Samsung Air Conditioner Error Code P405

P405 is a freeze protection fault code indicating that the indoor unit's heat exchanger temperature dropped to -4°C or below and stayed there for more than 40 seconds. The control board triggered this code to shut the system down and prevent ice buildup from damaging the unit. The most common causes are restricted airflow from a dirty filter or blocked grilles, but refrigerant or electrical issues can also be responsible.

A power reset may temporarily clear the P405 code, but the error will return if the underlying cause is not addressed. Simply resetting without resolving the airflow or refrigerant issue means the coil will freeze again and the fault will reappear, potentially within minutes of restarting. Always correct the root cause before relying on a reset.

If the fix is simply cleaning the air filter or clearing an obstruction, there is no parts cost involved. If the blower motor needs replacement, parts and labor typically range from $150 to $400 depending on the unit model and local labor rates. A refrigerant leak repair and recharge can range from $200 to $600 or more, depending on the severity of the leak and the amount of refrigerant required.

Start by turning off the unit and allowing any ice on the coil to fully thaw, which can take one to several hours. Then clean or replace the air filter and remove any obstructions around the indoor unit. If the error returns after restarting with clean filters and clear airflow, a technician should check the blower motor operation, refrigerant pressures, and thermistor function.

No, you should not continue running the unit while P405 is active. A frozen evaporator coil blocks airflow, causes water to leak as the ice melts, and forces the compressor to operate under abnormal conditions that can lead to compressor failure. The system's automatic shutdown is a protective measure that should be respected until the problem is resolved.