Freezer
F4
The F4 error code on an LG freezer indicates a fault with the freezer compartment sensor (ice maker sensor or freezer temperature sensor, depending on model) — it’s a moderately serious fault that will affect your freezer’s ability to maintain the correct temperature if left unresolved.
What does this error mean?
F4 on an LG freezer signals that the control board has detected an open circuit or out-of-range reading from the freezer compartment temperature sensor (also called the evaporator or ice maker sensor on some models). The board can no longer accurately monitor the freezer temperature, so it triggers the error to prevent food spoilage or compressor damage. In plain terms: the freezer’s thermometer is either broken, disconnected, or sending back a reading that makes no sense.
Est. repair cost
£15–£35 DIY sensor replacement; £80–£150 for a professional sensor repair; £150–£220 for a PCB repair fitted by an engineer
🔍 Likely causes
🛠️ Step-by-step fix
Reset the freezer: unplug it from the mains, wait 5 minutes, then plug back in. If F4 disappears, monitor for 24 hours — a one-off power glitch can trigger false codes.
Check for excessive ice build-up: if the back wall or floor of the freezer compartment is heavily frosted, run a manual defrost (unplug, empty contents into a cool bag, leave the door open for 2–3 hours). Heavy ice can encase the sensor and cause incorrect readings.
Locate the freezer temperature sensor: on most LG freestanding and American-style freezers, it sits on or near the evaporator coils behind the rear interior panel. Consult your model’s user manual or the LG UK support site (lg.com/uk) for the exact location.
Inspect the sensor and its wiring: with the freezer unplugged, carefully remove the rear interior panel (usually 4–6 screws). Check the sensor connector is fully seated and look for any visible corrosion, burn marks, or broken wires. Reseat any loose connections firmly.
Test the sensor with a multimeter (if you own one): a healthy LG freezer thermistor typically reads around 5–10 kΩ at 0°C. A reading of infinite resistance (open circuit) or zero confirms a failed sensor. Replacement thermistors for LG freezers cost £15–£35 from UK appliance parts suppliers such as eSpares or 4ourhouse.
Replace the sensor if confirmed faulty: unclip the old sensor, fit the new one in the same position, reconnect the wiring plug, refit the panel, and restore power. If the F4 code returns after a confirmed sensor replacement, the issue is likely the PCB — stop and call a technician.
📞 When to call a professional
If the F4 code returns after a successful sensor replacement, or if you find burn marks, melted wiring, or signs of electrical damage inside the compartment, stop and contact an appliance engineer — do not attempt to repair PCB-level faults yourself. When you call, tell the engineer: ‘My LG freezer is displaying error code F4, I’ve already checked/replaced the freezer thermistor and the code has returned’ — this will save diagnostic time and likely reduce your call-out cost.
⚖️ Repair or replace?
A sensor replacement is a cost-effective repair on any freezer under 8 years old — the part is cheap and the job is straightforward for a confident DIYer or an engineer. If your LG freezer is over 8–10 years old and the fault turns out to be a PCB failure (typically £120–£200 fitted), weigh that against the cost of a comparable new LG freezer (£300–£600); replacement is often the smarter financial call. For freezers under 5 years old, always repair first.