LG Heat Pump Error Code E172

E172 indicates that during the system's piping check routine, an unexpected change was detected in the evaporator inlet temperature of one of the indoor units that was not supposed to be actively receiving refrigerant flow. This points to a problem with refrigerant distribution, an expansion valve, a temperature sensor, or system configuration in a multi-zone setup. The piping check is a diagnostic sequence the system runs to verify correct refrigerant circuit operation, so this fault means that verification failed.

When E172 is active, the system has flagged a problem with refrigerant distribution that was detected during the piping check. Continuing to operate the system without resolving the issue could result in inefficient operation, inadequate heating or cooling, or potential stress on compressor and valve components. It is advisable to stop the piping check sequence and have the system inspected before resuming normal operation.

Repair costs vary depending on the root cause identified. Diagnostic service calls alone can range from around 80 to 150 dollars. If an electronic expansion valve needs replacement, parts and labor combined can range from 200 to 600 dollars or more depending on the unit model. Refrigerant-related repairs involving charge adjustment may add further costs, especially if a leak is found and must be located and repaired first.

Most of the root causes behind E172 require professional diagnosis and repair. Checking and adjusting refrigerant charge, testing electronic expansion valves, and reconfiguring system addressing all require specialized tools and training. A homeowner can check that all communication wiring connections are secure and that no indoor unit has been physically obstructed, but resolving the fault itself will typically require a certified HVAC technician.

A reset may temporarily clear the E172 fault display, but if the underlying issue such as a faulty EEV, refrigerant imbalance, or sensor problem is not corrected, the error will return the next time a piping check is performed. Resetting without diagnosis does not address the root cause and the system will continue to fail the piping verification routine.