LG Air Conditioner Error Code 118

Error code 118 indicates that the Sub1 outdoor unit air temperature sensor is reading as open or shorted. The control board has detected a resistance value from the sensor that falls outside the acceptable range for normal thermistor operation. This prevents the system from accurately monitoring outdoor air temperature, which is required for proper operation. The fault may be in the sensor itself, its lead wire, or the connector.

Running the unit with an active 118 error is not recommended. Without a functioning outdoor air temperature sensor, the control system cannot make accurate decisions about operation, which can lead to inefficient performance or protective shutdowns. Continuing to operate the system in this condition may place additional stress on other components. It is best to address the sensor fault before resuming normal use.

A power reset may temporarily clear the error code, but if the underlying fault with the sensor, lead wire, or connector has not been corrected, the code will return once the system runs its diagnostic checks again. A reset is useful for confirming whether the fault is intermittent, but it is not a repair. The physical condition of the sensor and its wiring must be inspected and corrected to permanently resolve the error.

Start by powering off the unit and inspecting the temperature sensor connector and lead wire on the outdoor unit for visible damage, corrosion, or loose connections. Reseat the connector firmly and clear any corrosion from the terminals. If the wiring appears intact, use a multimeter to measure the resistance across the sensor terminals and compare it to the expected value for the current ambient temperature. If the sensor reads open or shorted, it will need to be replaced.

If the fix is simply reseating a loose connector or cleaning corroded terminals, the cost may only involve a service call fee, typically in the range of $75 to $150. If the thermistor sensor requires replacement, parts are generally low-cost components, but total repair cost including labor can range from $100 to $300 depending on the technician's rates and the specific unit configuration. Control board replacement, if required, would increase costs significantly.