LG Heat Pump Error Code E173

E173 means the system detected an unexpected change in the evaporator outlet temperature on one of the indoor units while running its piping check routine. This check is designed to verify that refrigerant is flowing correctly through each zone, and a temperature shift on an inactive unit indicates something is wrong with refrigerant flow or a temperature sensor. The fault is specific to multi-zone LG heat pump systems and requires identifying which indoor unit is affected.

Running the system while E173 is active is not recommended. Unintended refrigerant flow through an inactive indoor unit can lead to uneven system performance, potential compressor stress, and further damage to expansion valves or sensors. It is best to stop operation and have the system inspected before resuming regular use.

A reset may temporarily clear the E173 code, but the error will return the next time the system runs a piping check if the underlying problem has not been resolved. Resetting without addressing the cause is not a permanent fix and could mask a condition that leads to more serious damage over time.

Some basic checks, such as verifying wiring connections, indoor unit address settings, and piping configuration, can be done by a knowledgeable DIYer. However, diagnosing a faulty expansion valve or checking refrigerant pressures and charge levels requires specialized tools and EPA refrigerant handling certification, so a licensed HVAC technician is typically needed for a complete repair.

Repair costs depend on the root cause. A thermistor replacement is generally on the lower end, typically in the range of $100 to $300 including parts and labor. An electronic expansion valve replacement can run $300 to $700 or more depending on the unit. Refrigerant recharge or piping corrections may add additional cost depending on the extent of work required.