LG Air Conditioner Error Code 164

Error code 164 means the front-side heat exchanger temperature sensor (A) on the sub3 outdoor unit is reading an open or short circuit condition. The control system cannot get a valid temperature reading from this thermistor, so it logs the fault and may limit or shut down operation. Diagnosis should follow the CH45 sensor fault procedure, which involves checking sensor resistance, wiring continuity, and connector condition.

Running the system with an active sensor fault is not advisable. The heat exchanger temperature sensor is used for refrigerant flow control, coil protection, and defrost management. Operating without a valid sensor reading can lead to coil freeze-up, refrigerant flooding the compressor, or overheating, any of which can cause more serious and costly damage to the outdoor unit.

A power reset may temporarily clear the fault code, but it will return as soon as the system restarts and detects the same invalid sensor signal. Error code 164 reflects an underlying hardware condition, either a failed sensor, damaged wiring, or a bad connector, that must be physically corrected before the code will stay cleared. Repeated resets without addressing the root cause will not resolve the problem.

Some basic checks are accessible to a knowledgeable DIYer, such as inspecting visible wiring and connectors on the outdoor unit for obvious damage or corrosion. However, properly diagnosing the sensor resistance against its rated curve, and working inside an outdoor unit on a multi-zone VRF system, generally requires tools and training that most homeowners do not have. A certified HVAC technician is recommended for a complete diagnosis and repair.

Repair costs depend on the root cause. A simple connector cleaning or wiring repair might cost between $75 and $200 in labor. Replacing the thermistor sensor itself is typically a low-cost part, with total repair costs ranging from $100 to $350 depending on labor rates and accessibility. If the outdoor control board needs replacement, costs can range from $400 to $900 or more, including parts and labor.