Samsung Heat Pump Error Code E518

E518 indicates an open or short circuit fault in the dual-pipe temperature sensor. This sensor is a thermistor that measures refrigerant temperature at the dual-pipe section of the system and feeds that data to the control board. When the sensor signal falls outside the expected resistance range, the board logs E518 and may restrict or stop operation to protect the system.

A reset may temporarily clear the error code, but if the underlying sensor fault still exists, E518 will return once the unit cycles back through its diagnostic checks. The root cause, whether a loose connector, failed sensor, or damaged wiring, must be corrected for the fault to stay cleared. Repeated resets without repair can mask the problem and potentially affect system performance or protection functions.

Repair costs vary depending on what is faulty. If the fix is simply reseating a connector, the cost may only be a service call fee, typically in the range of $75 to $150. Replacing the dual-pipe temperature sensor itself is a relatively low-cost part, with total repair estimates generally ranging from $100 to $300 including labor. If the PCB requires replacement, costs can rise significantly, often falling in the $300 to $700 range or higher depending on the model.

A knowledgeable DIYer can check whether the sensor connector has come loose from the PCB and reseat it, which is the first recommended diagnostic step. Testing sensor resistance with a multimeter is also within reach for someone comfortable with basic electrical checks. However, if the sensor, wiring harness, or PCB needs replacement, working on refrigerant-side components or control boards is best left to a certified technician.

Operating the unit continuously with an active E518 fault is not recommended. The dual-pipe temperature sensor provides data used for defrost cycles and refrigerant protection logic. Without accurate sensor readings, the system may not defrost properly or may fail to protect itself from abnormal operating conditions, potentially leading to compressor or refrigerant circuit damage over time.