Samsung Heat Pump Error Code E402

E402 indicates that the indoor heat exchanger EVAP IN temperature sensor has detached from the refrigerant inlet pipe on the evaporator coil. This sensor is a thermistor that must be in direct contact with the pipe to read accurate temperatures. When it separates, the control board receives out-of-range temperature data and triggers the E402 fault to protect the system.

Running the unit while E402 is active is not recommended. Without accurate evaporator inlet temperature data, the control board cannot properly manage freeze protection or defrost cycles, which could lead to coil icing or compressor stress. The system will typically restrict or shut down operation on its own when this fault is present, so address the sensor issue before resuming normal use.

A power reset may temporarily clear the error display, but the fault will return quickly if the EVAP IN sensor is still detached or damaged. The underlying physical issue must be corrected first by reseating the sensor firmly against the inlet pipe. Only after the sensor is properly secured and reading within a normal temperature range will the E402 code stay cleared.

In many cases, yes. The first step is to access the indoor unit, locate the EVAP IN sensor on the inlet side of the evaporator coil, and check whether it has come loose from the pipe. If it has simply detached, repositioning it against the pipe and securing it with foam tape or the original retaining clip may resolve the fault without any tools or replacement parts. If the sensor is damaged or the error persists after reattachment, a technician should verify sensor resistance values and replace the thermistor if needed.

If the sensor only needs to be reattached, the repair cost is minimal, typically covering just the service call fee in the range of $75 to $150. If the thermistor itself is damaged and requires replacement, parts and labor combined generally fall in the range of $100 to $300 depending on your location and the technician's rates. The repair is straightforward and usually completed in a single visit.