Samsung Air Conditioner Error Code E355

E355 is a thermal protection error triggered when the Intelligent Power Module (IPM) associated with the second fan motor (Fan2) reaches an excessive temperature. The IPM is a compact power electronics module that controls the fan motor's operation by regulating voltage and switching frequency. When the module's internal temperature sensor detects overheating beyond the safe threshold, the system halts operation and logs E355 to prevent permanent damage to the IPM or connected circuitry.

The most common root cause of IPM overheating is inadequate thermal transfer between the IPM and its heat sink. The heat sink assembly is designed to draw heat away from the module during operation, but if the thermal interface material has degraded, if the heat sink is clogged with dust or debris, or if a foreign object is blocking airflow across the fins, heat accumulates rapidly. Samsung's first diagnostic step specifically targets this assembly because restricted heat dissipation is the leading contributor to this fault.

Additional causes can include a failing or seized Fan2 motor drawing excess current through the IPM, causing elevated internal power dissipation. Ambient conditions such as extreme outdoor temperatures or poor ventilation around the unit can compound thermal stress. In some cases, the IPM itself is damaged or has degraded thermal characteristics and will overheat even when cooling conditions are adequate. A thorough inspection should cover the heat sink fins, the thermal pad or compound, the fan blade for obstruction or drag, and airflow clearances around the unit.