LG Air Conditioner Error Code CH31

CH31 on an LG air conditioner indicates a CT error, meaning the current transformer sensor has detected abnormally low electrical current in the system. The control board monitors current draw through this sensor to confirm that key components like the compressor are operating correctly. When current falls below the expected range, the unit logs this fault and may shut down. A technician should inspect the CT sensor, its wiring, and the compressor circuit to identify the cause.

Operating the unit while CH31 is active is not advisable. The error indicates that the system cannot confirm proper current flow, which may mean the compressor or another critical component is not functioning correctly. Continued operation under these conditions could lead to further component damage. The system should remain off until the fault is properly diagnosed and resolved.

Repair costs depend on which component is at fault. CT sensor replacement is generally one of the less expensive repairs, while compressor replacement is significantly more costly and can range from several hundred to over a thousand dollars including labor. Control board replacement falls somewhere in between. A diagnostic visit from an HVAC technician, which typically costs between $75 and $150, is the first step to determine exactly what needs to be replaced.

Some aspects of diagnosing CH31 are accessible to a knowledgeable DIYer, such as checking that all wiring connections to the CT sensor are secure and free of corrosion. However, testing the current transformer output, evaluating compressor function, and replacing control components involves working near high-voltage circuits, which carries serious safety risks. It is generally recommended to have a qualified HVAC technician handle the full diagnosis and repair.

A power reset by turning the unit off at the breaker for several minutes may temporarily clear the error display, but it will not fix the underlying problem. If the CT sensor, wiring, or compressor fault is still present, the CH31 code will return once the unit attempts to operate again. A proper repair addressing the root cause is required for the error to stay cleared.