LG Heat Pump Error Code P761

P761 is a reverse phase detection error for the outdoor unit on an LG heat pump. It means the control board has detected that the three-phase power supply is connected in an incorrect phase sequence. This is a protective lockout that prevents the compressor and fan motors from running in reverse, which could cause serious damage. The system will not operate until the phase sequence is corrected.

The P761 error code is a protective lockout, meaning the heat pump will not allow the outdoor unit to operate while the fault is active. This is intentional, as running a compressor in reverse rotation can cause rapid and severe mechanical damage. The system is effectively protecting itself, so there is no additional risk of damage from the fault being present. However, the error should be diagnosed and corrected promptly to restore heating or cooling.

If the cause is simply swapped phase conductors in the wiring, repair costs are typically limited to an electrician or technician service call, which can range from roughly $100 to $300 depending on your location and the time required. If the outdoor unit control board has failed and needs replacement, parts and labor costs can range from $300 to $800 or more depending on the specific model and part availability. Getting a diagnosis from a qualified technician first will help clarify the actual cause before committing to parts.

Correcting a reverse phase error involves working with three-phase electrical power at the outdoor unit, which presents a serious shock and arc flash hazard. The repair typically requires swapping two of the three phase conductors at the outdoor unit terminal block or disconnect, and verifying the correct sequence with a phase sequence meter. This work should be performed by a licensed electrician or certified HVAC technician. DIY attempts on three-phase wiring are not recommended without proper training and equipment.

A simple power reset will not clear the P761 error if the underlying phase sequence problem has not been corrected. The outdoor unit's control board checks the phase sequence each time the system is powered on, and will re-trigger the fault if it detects the same reversed phase condition. The error will only clear once the incoming three-phase power is correctly sequenced and the control board verifies this at startup.