LG Heat Pump Error Code P520

The P520 code means the outdoor unit's second Electronic Expansion Valve (EEV) has failed its open position self-diagnostic test. The system commands the valve to open, and when the expected response is not detected, this fault is triggered. It points to a problem with the EEV itself, its wiring, or the outdoor control board. The heat pump will not operate normally until the fault is resolved.

Running the heat pump with an active P520 fault is not recommended. A malfunctioning EEV can cause improper refrigerant flow, which can stress or damage the compressor over time. The system may also operate with significantly reduced efficiency or fail to provide heating or cooling output. It is best to shut the unit down and have a technician diagnose it promptly.

Repair costs vary depending on the root cause. An EEV coil or wiring repair might fall in the range of $150 to $350 including labor, while replacing the full EEV assembly can range from $300 to $700 or more depending on the model and labor rates in your area. If the outdoor control board is the cause, board replacement typically ranges from $400 to $900 including parts and labor. Getting a diagnosis from a certified technician before committing to any repair is always advisable.

Resolving P520 typically requires a qualified technician because it involves diagnosing electrical signals, checking wiring continuity, and potentially handling refrigerant system components. A homeowner can visually inspect the outdoor unit wiring for obvious damage or loose connectors, but component-level diagnosis and replacement should be handled by a certified HVAC technician. Attempting repairs without proper tools and training can cause further damage or safety hazards.

A power reset may temporarily clear the P520 code, but it will almost always return if the underlying fault is not corrected. The self-diagnostic routine runs each time the unit starts or cycles, so a failed EEV, damaged wiring, or faulty PCB will trigger the code again shortly after the reset. Persistent recurrence after a reset is a strong indicator that a component needs to be inspected or replaced.