LG Refrigerator Error Code F-18

The F-18 code indicates a Freezer Room Sensor (F-Sensor) error. The main control board is receiving a signal from the freezer thermistor that is outside the valid voltage range of 1.0V to 4.5V at connector CN30. This can be caused by a displaced sensor, damaged wiring, or a failed sensor that is reading temperatures above 149 degrees F or below -58 degrees F.

It is not advisable to rely on the refrigerator for long-term food storage while F-18 is active. Because the freezer temperature sensor is not functioning correctly, the control board cannot accurately regulate freezer temperatures, which could lead to food spoilage or inadequate freezing. Address the fault as soon as possible.

A power reset may temporarily clear the F-18 code from the display, but the error will return if the underlying fault is not corrected. The code is triggered by an ongoing out-of-range signal from the sensor circuit, so a reset alone does not fix a displaced sensor, damaged wire, or failed thermistor. The root cause must be diagnosed and repaired for the code to stay cleared.

Some causes of F-18 are DIY-friendly, such as reseating a sensor that has slipped from its housing or reseating a loose connector. Wiring repairs and sensor replacement require basic electrical knowledge and comfort working inside a refrigerator. If you are not confident testing voltage at the main PCB or handling wiring repairs, a qualified technician is recommended.

If only a connector reseating or sensor repositioning is needed, the repair may cost nothing beyond your time. A replacement freezer room sensor part typically ranges from around $15 to $50 depending on the model. If a technician is needed for diagnosis and repair, expect total service costs in the range of $100 to $250 or more, depending on your location and what parts are required.