LG Heat Pump Error Code P502

P502 indicates that the heat pump's high-side discharge pressure remained at or below 9 kg/cm² (approximately 128 psi) for 10 continuous minutes. This triggers a protective shutdown to prevent compressor damage. The fault points to a problem in the refrigerant circuit, such as a low charge, a restriction, or a compressor issue.

No. The unit has shut itself down specifically to protect the compressor from operating under abnormal pressure conditions. Attempting to bypass or repeatedly reset the unit without addressing the underlying cause can lead to compressor failure, which is one of the most costly repairs on a heat pump system.

Repair costs vary widely depending on the root cause. Refrigerant leak detection and recharge can range from $200 to $600 or more depending on the refrigerant type and amount needed. A replacement expansion valve or filter drier typically falls in the $150 to $400 range including labor. Compressor replacement is significantly more expensive, often ranging from $800 to $2,000 or higher depending on the unit size and refrigerant type.

Some basic checks, such as inspecting the outdoor unit for ice buildup, debris blocking the coil, or a non-spinning fan, can be done without special tools. However, diagnosing refrigerant charge issues, locating leaks, and recharging the system require EPA certification and professional manifold gauge equipment. Compressor and expansion valve diagnosis also requires a qualified technician.

A power reset may temporarily clear the fault and allow the unit to restart, but if the underlying condition causing low discharge pressure has not been corrected, the P502 code will return once the system runs for 10 minutes under the same low-pressure condition. A reset without diagnosis is not a fix.