Samsung Heat Pump Error Code E502

E502 indicates an open or short circuit fault on the indoor unit EVAP IN sensor, which is the thermistor that measures refrigerant temperature at the evaporator inlet. The control PCB is receiving a resistance value outside the acceptable range and cannot determine the actual temperature at that point. The system flags this fault to prevent operating on bad sensor data, which could lead to coil icing or refrigerant management errors.

Running the system with an active E502 fault is not recommended. The evaporator inlet sensor data is used to manage refrigerant flow and prevent coil icing. Without reliable sensor input, the system may operate inefficiently or cause secondary damage to the compressor or other components. Most Samsung heat pumps will limit or suspend operation automatically when this code is active.

Repair costs depend on the root cause. If only the connector needs reseating, there may be no parts cost and just a service call fee, which typically ranges from $75 to $150. If the EVAP IN sensor requires replacement, the part itself generally costs between $20 and $80, and total repair costs including labor can range from $100 to $300. PCB replacement, if needed, is more expensive and can bring total costs to $300 or higher depending on the model and labor rates in your area.

Some steps are accessible to a knowledgeable DIYer. You can remove the indoor unit cover, locate the EVAP IN sensor connector on the PCB, confirm it is fully seated, and use a multimeter to measure resistance across the sensor terminals. If the connector was simply loose and the sensor tests normally, reseating it may resolve the error. However, if the sensor has failed or the wiring is damaged, replacement involves working near electrical components and refrigerant lines, which may be better handled by a qualified technician.

A power reset may temporarily clear the fault code, but if the underlying sensor fault is still present, the E502 error will return once the system restarts and the PCB polls the sensor again. A reset alone is not a fix. The sensor, its connector, and its wiring harness need to be inspected and tested before the error can be permanently resolved.