LG Air Conditioner Error Code 171

Error code 171 indicates that the input voltage at the sub3 outdoor unit in your LG system is outside the acceptable operating range. For three-phase systems, the allowable range is 380V plus or minus 10% (342V to 418V). For single-phase systems, the allowable range is 220V plus or minus 10% (198V to 242V). The system shuts down to prevent electrical damage to the compressor and other components.

Yes, this code represents a real electrical safety issue. Voltage that is too high can damage or destroy compressors, capacitors, and control boards. Voltage that is too low can cause motors to draw excessive current and overheat. The system correctly protects itself by shutting down, but the underlying power problem should be corrected promptly to avoid equipment damage or a fire hazard.

Repair costs vary widely depending on the cause. If the issue is a utility-side voltage problem or a loose connection, costs may be limited to a service call fee in the range of $100 to $200. If wiring needs to be replaced or a circuit board has been damaged by the voltage event, costs can range from $300 to over $1,000 including parts and labor. A licensed technician can provide a more accurate estimate after diagnosing the specific fault.

Diagnosing and repairing this fault requires working with high-voltage electrical systems, which should only be performed by a licensed HVAC technician or electrician. A technician will follow the CH25 troubleshooting procedure, measure actual supply voltages under load, and inspect wiring and connections. Attempting to work on the electrical supply without proper training and equipment is dangerous.

A reset may temporarily clear the fault display, but the error will return immediately if the supply voltage is still outside the acceptable range. The root cause must be identified and corrected before the system will operate normally. Repeatedly resetting a unit with an active voltage fault risks damaging the compressor and electrical components.