LG Air Conditioner Error Code 159

Error code 159 on an LG air conditioner indicates that the Sub3 air temperature sensor on the outdoor unit is reading as open or shorted. This means the control board cannot get a valid temperature reading from that sensor. The unit will limit or stop operation until the fault is resolved. The issue typically lies with the sensor connection, the sensor itself, or the wiring harness.

It is not recommended to continue running the unit while error code 159 is active. The outdoor unit relies on the Sub3 sensor data for safe temperature monitoring and operational decisions. Running the system without accurate sensor feedback could lead to improper operation or additional component stress.

A power reset may temporarily clear the error display, but if the underlying sensor fault still exists, the code will return once the unit restarts and attempts to read the Sub3 sensor. A reset alone does not fix the root cause. The sensor connection, sensor resistance, and wiring should all be inspected and addressed before relying on normal operation.

Some basic checks are within reach for a knowledgeable DIYer, such as inspecting and reseating the sensor connector at the outdoor unit PCB. However, testing thermistor resistance and inspecting internal wiring requires a multimeter and comfort working around electrical components with power disconnected. Replacing the sensor or PCB is best handled by a certified technician.

If only the sensor needs replacement, repair costs typically range from roughly 80 to 200 dollars including parts and labor. If the wiring harness is damaged, costs may be similar but vary with the extent of the repair. A failed outdoor unit PCB is the most expensive scenario, with total repair costs potentially ranging from 300 to 600 dollars or more depending on the model and labor rates in your area.