LG Air Conditioner Error Code 166

Error 166 on an LG air conditioner indicates that the liquid pipe temperature sensor on the condenser of the sub3 outdoor unit has been detected as open or shorted. This means the control board is not receiving a valid signal from that thermistor. The system shuts down to prevent operating without accurate refrigerant temperature data. A technician will need to test the sensor resistance and inspect the associated wiring.

No, it is not advisable to continue operating the system while error 166 is active. The liquid pipe sensor provides data the system uses to protect the compressor and manage refrigerant flow. Running the unit without a valid sensor signal could lead to improper refrigerant management and potential compressor damage over time.

A power reset may temporarily clear the error and allow the unit to attempt restarting, but if the underlying sensor fault is still present, the code will return quickly. Error 166 reflects an active hardware fault, not a temporary glitch, so resetting without addressing the root cause will not resolve the problem. A proper repair of the faulty sensor or wiring is required to permanently clear the fault.

Some basic checks, such as inspecting visible wiring for damage or reseating loose connectors, can be done without specialized tools. However, accurately diagnosing a thermistor failure requires a multimeter and knowledge of resistance-temperature specifications. Replacing components in a multi-unit outdoor system also involves working near refrigerant circuits and high-voltage components, so professional service is strongly recommended for most homeowners.

Repair costs vary depending on whether the issue is a simple connector problem or requires replacing the thermistor or wiring harness. A thermistor sensor replacement on an outdoor unit typically falls in the range of 150 to 400 dollars including parts and labor. If the control board is involved, costs can be higher, generally in the 300 to 700 dollar range depending on parts availability and labor rates in your area.