LG Heat Pump Error Code P753

P753 indicates that the outdoor unit's third electronic expansion valve (EEV) has failed its open-position self-diagnosis test. The heat pump runs a routine check to confirm each EEV responds correctly to control commands, and EEV 3 did not pass. This points to a fault in the valve coil, wiring harness, or the outdoor control board's driver circuit.

Operating the system with an EEV fault is not advisable. A malfunctioning expansion valve can cause improper refrigerant flow, which may lead to compressor damage over time due to liquid slugging or insufficient lubrication. The unit should be serviced promptly to avoid more costly secondary damage.

Repair costs vary depending on the root cause. If only wiring or connector work is needed, a technician visit may cost in the range of $100 to $250. An EEV replacement typically adds $150 to $400 or more in parts, while an outdoor control board replacement can bring total costs into the $400 to $900 range or higher depending on labor rates and the specific model.

Basic checks such as inspecting and reseating the EEV wiring harness connector can be performed by a knowledgeable DIYer. However, testing coil resistance, diagnosing control board output signals, and replacing the EEV all require refrigerant system knowledge and proper tools. It is strongly recommended to contact a licensed HVAC technician for this repair.

A power reset may temporarily clear the code, but if the underlying fault in the EEV coil, wiring, or control board is still present, the error will return once the system runs its self-diagnosis again. A reset alone does not repair the component causing the fault and should not be used as a substitute for proper diagnosis.