LG Heat Pump Error Code P504

P504 indicates an outdoor unit overload 1 protection control error. The heat pump's protection circuit has detected that the outdoor unit, most likely the compressor, is operating under conditions that exceed safe limits for current or temperature. The system shuts down to prevent component damage. A technician should inspect refrigerant pressures, airflow, and compressor health to find the root cause.

No, you should not continue running the unit while P504 is active. The overload protection circuit exists to prevent serious damage to the compressor, which is the most expensive component in the outdoor unit. Forcing the system to run through repeated overload events can cause permanent compressor failure. Leave the unit off until the underlying cause has been diagnosed and corrected.

Repair costs vary widely depending on the cause. A coil cleaning or voltage correction may cost between $75 and $200 for a service call. A refrigerant recharge or leak repair typically ranges from $150 to $500 or more depending on refrigerant type and the amount needed. Compressor replacement is the most expensive scenario, generally ranging from $800 to $2,500 or higher depending on unit size and labor rates in your area.

Some causes, like a blocked outdoor coil, can be addressed by a knowledgeable homeowner by cleaning the unit and removing debris from around it. However, diagnosing refrigerant pressure issues, testing compressor windings, and replacing components such as a compressor or overload protector require specialized tools and EPA certification for refrigerant handling. Most repairs beyond basic cleaning should be handled by a licensed HVAC technician.

A power reset may temporarily clear the error and allow the unit to restart, but if the underlying cause is not corrected, the fault will return. In some cases it returns quickly at the next startup attempt. Resetting without diagnosing the root cause risks repeated stress on the compressor and can accelerate its failure. Always identify and correct the cause before relying on a reset as a solution.