LG Air Conditioner Error Code E503

E503 on an LG air conditioner is an alert indicating that the system has detected a service valve may be in the closed position. Service valves are the refrigerant shutoff valves located on the outdoor unit. The code is designed to warn users before the system operates with restricted or blocked refrigerant flow, which could cause serious damage to the compressor.

No, you should not continue running the unit while E503 is active. If a service valve is closed, the compressor could be operating with severely restricted or no refrigerant flow, which can cause compressor overheating and permanent damage. Address the valve condition before attempting to run the system.

If the cause is simply a closed service valve from installation or recent service work, there is no parts cost and a technician visit, if needed, would typically run in the range of $75 to $150 for a diagnostic call. If the error is caused by a faulty pressure sensor or control board, parts and labor costs could range from $150 to $500 or more depending on the specific component involved.

Locate the service valves on the outdoor unit, typically found at the refrigerant line connections. Remove the valve caps and turn each valve stem fully counterclockwise to open them completely. Replace the caps securely and then restart the unit. If the error clears, the system should operate normally.

A simple power reset will not permanently clear E503 if the underlying service valve condition has not been corrected. The error will return once the system attempts to operate and detects the same problem. The service valves must be physically confirmed in the open position before the code will clear and stay clear.