Freezer
F3
The F3 error code on an LG freezer indicates a fault with the freezer compartment sensor (defrost sensor or temperature sensor), meaning the appliance can no longer accurately monitor its internal temperature. It’s a moderately serious fault — your freezer may continue running, but food safety is at risk if left unresolved.
What does this error mean?
The F3 code signals that the freezer’s temperature sensor (also called a thermistor) is either reading an out-of-range temperature or has failed entirely. LG’s control board uses this sensor to regulate the compressor and defrost cycles — without a reliable reading, the freezer can’t maintain safe temperatures. In some LG models, F3 specifically points to the defrost sensor circuit rather than the main cabinet thermistor, but both sit in the same diagnostic category.
Est. repair cost
£10–£25 DIY thermistor part; £80–£130 professional thermistor repair; £150–£250 if control board replacement is needed
🔍 Likely causes
🛠️ Step-by-step fix
Hard reset the freezer: unplug it from the wall socket, wait 5 full minutes, then plug back in. If F3 clears and doesn’t return within a few hours, the fault may have been a temporary sensor glitch.
Inspect the door seal: run your fingers around the full perimeter of the freezer door seal, feeling for gaps, tears, or sections that don’t spring back. A failing seal is an easy, cheap DIY fix — replacement seals for LG freezers cost £15–£35 online and clip or press into place.
Defrost the freezer manually: unload food into a cool bag, switch the unit off, and leave the door open for 24 hours with towels on the floor. Excessive ice build-up around the sensor can trigger F3 — if the code disappears after a full defrost, ice was the culprit.
Locate and inspect the thermistor: on most LG fridge-freezers it sits behind the rear panel inside the freezer compartment. Remove stored items and any shelving, then unscrew the back panel (typically 4–6 Torx or Phillips screws). Check the sensor and its wiring connector for visible damage, ice damage, or a loose plug — reseat the connector firmly.
Test or replace the thermistor: with a multimeter set to resistance (Ω), test the thermistor at room temperature — a healthy LG freezer thermistor typically reads around 5,000–10,000 ohms at 0°C. If it reads open circuit (OL) or near zero, it has failed. Replacement thermistors for LG models are widely available for £10–£25; match your model number exactly.
If the thermistor and wiring check out fine, do not attempt to replace or repair the main control board yourself — this requires specialist diagnostic equipment and carries a risk of making the fault worse. Stop here and call an engineer.
📞 When to call a professional
Call an appliance engineer if the F3 code returns after a hard reset and manual defrost, or if you’ve confirmed the thermistor has failed but aren’t comfortable replacing it yourself. Tell the engineer: ‘My LG freezer is showing an F3 error code — I believe it’s a thermistor or defrost sensor fault.’ If the fault points to the main control board, professional repair is essential. Find a Which? Trusted Trader or a Domestic & General-approved engineer for LG appliances.
⚖️ Repair or replace?
A thermistor replacement by a professional typically costs £80–£130 all-in for parts and labour in the UK — well worth it if your freezer is under 8 years old. If the control board has failed, repair quotes rise to £150–£250, at which point a freezer over 7–8 years old is often better replaced; a decent 200-litre freestanding freezer starts at around £250–£350. For freezers under 5 years old, always repair first.