LG Heat Pump Error Code P518

P518 means the outdoor unit's discharge temperature has reached a level that triggered Protection Control 3, causing the system to shut down to prevent compressor damage. The discharge temperature is the temperature of refrigerant gas exiting the compressor. This protection activates when the temperature exceeds a defined safety threshold. The underlying cause must be identified and corrected before normal operation can resume.

No, you should not attempt to bypass or ignore the P518 error. The system has shut down to protect the compressor from heat-related damage, and continued operation under fault conditions can cause permanent compressor failure. Leave the unit off until the fault has been properly diagnosed and repaired.

Repair costs vary widely depending on the cause. A condenser coil cleaning may cost between $75 and $200. Refrigerant recharge, including leak detection and repair, can range from $200 to $600 or more. A discharge temperature sensor replacement typically falls between $100 and $300 including labor. Compressor replacement is the most expensive scenario, often ranging from $1,200 to $2,500 or higher depending on the model and labor rates.

Some causes, such as a dirty condenser coil or debris blocking the outdoor unit, can be addressed by a homeowner through cleaning and clearing the area around the unit. However, refrigerant issues require an EPA-certified technician, and electrical or sensor diagnostics require proper test equipment. Attempting to add refrigerant or manipulate the refrigerant circuit without certification is illegal and unsafe. It is generally recommended to have a qualified HVAC technician perform the full diagnosis.

A power reset may temporarily clear the error code and allow the unit to restart, but if the underlying cause is not corrected, the P518 fault will return, often quickly. Repeated fault cycles without repair increase the risk of compressor damage. A reset should only be used as part of a diagnostic process, not as a substitute for repair.