Freezer
F1
The F1 error code on an LG freezer indicates a fault with the freezer’s temperature sensor (also called a thermistor), meaning the appliance can no longer accurately read the internal temperature. While it sounds alarming, it’s one of the more common LG freezer faults and is sometimes fixable without calling an engineer. In this guide, you’ll learn exactly what triggers the F1 code, the most likely causes, safe DIY steps to try first, and honest advice on when it’s time to call a professional.
What does this error mean?
On LG freezers — including models in the LG GSJ, GBB, and GML ranges — the F1 error code signals that the freezer compartment temperature sensor (thermistor) has failed, become disconnected, or is sending a reading that falls outside the expected range. The thermistor is a small electrical component, usually clipped to the evaporator coil inside the freezer, that continuously monitors the internal temperature and feeds that data to the main control board. When the board receives a reading that’s implausibly high, implausibly low, or simply no reading at all, it throws the F1 code and may reduce or stop cooling to prevent further damage. In practical terms: your freezer knows something is wrong with its temperature monitoring system, and it’s telling you. Your food may still be frozen for now, but the appliance cannot guarantee safe temperatures until the fault is resolved.
Est. repair cost
DIY thermistor replacement: £10–£25 for the part. Professional repair (call-out, diagnosis, and thermistor replacement): £80–£140. Main control board replacement by an engineer: £160–£280 including parts and labour.
🔍 Likely causes
🛠️ Step-by-step fix
Step 1 — Reset the freezer: Unplug the appliance from the wall socket (or switch off at the fuse spur), wait a full 10 minutes, then restore power. This clears temporary error states caused by power surges or minor sensor glitches. If the F1 code disappears and does not return within 24 hours, no further action is needed — but monitor closely.
Step 2 — Check your door seals: Close the freezer door on a piece of paper (an A4 sheet works well). If you can pull the paper out easily without resistance, the door seal is worn. A failing seal lets warm air in, causes temperature swings, and stresses the sensor. Replacement LG door seals typically cost £20–£45 and can be fitted without tools by pressing the new seal into the door channel.
Step 3 — Inspect for excessive ice build-up: Open the freezer and check whether the back wall or bottom is coated in a thick layer of ice (more than a centimetre). If so, the defrost system may have been struggling. Remove all food, place towels at the base, and allow the freezer to defrost fully with the door open — this can take 4–8 hours. Once defrosted, restart and see if the F1 code returns.
Step 4 — Locate and visually inspect the thermistor (safe visual check only): On most LG freezers, the thermistor is a small clip-on probe attached to the evaporator coil, accessed by removing the interior back panel (usually held in place by 2–4 Phillips-head screws — no tools beyond a screwdriver required). Look for obvious damage: cracked casing, visible corrosion, or a wire that has clearly come loose from its connector. Do not probe or handle electrical connectors unless the appliance is fully unplugged.
Step 5 — Check the thermistor wiring connector: With the appliance unplugged, locate the wire harness running from the thermistor to the back of the freezer cabinet. Gently press the connector plug firmly into its socket — it should click securely. A partially seated connector is a surprisingly common cause of intermittent F1 codes and costs nothing to fix.
Step 6 — Test the thermistor resistance (for confident DIYers with a multimeter): Disconnect the thermistor connector. Set a multimeter to the resistance (Ω) setting. At room temperature (around 20°C), a healthy LG freezer thermistor should read approximately 5,000–6,000 ohms (5–6 kΩ). A reading of zero (short circuit) or infinite resistance (open circuit) confirms a faulty sensor. Replacement LG thermistors are widely available in the UK for £10–£25 — search by your model number, found on the label inside the freezer door frame.
Step 7 — Replace the thermistor if confirmed faulty: With the appliance unplugged, unclip the old thermistor from the evaporator coil, disconnect the wiring harness, and clip the new sensor in its place. Reconnect the wiring, refit the back panel, restore power, and check whether the F1 code has cleared. No soldering or specialist skills are required — this is a plug-and-clip replacement.
Step 8 — If the code persists after a new thermistor: The fault likely lies in the wiring harness or the main control board. At this point, further DIY diagnosis requires access to internal electrical components and is not recommended for non-specialists. Stop here and contact an appliance engineer.
📞 When to call a professional
Call a qualified appliance engineer if: the F1 code returns immediately after a reset and a full manual defrost; you’ve replaced the thermistor and the code persists; your multimeter shows the thermistor is healthy (ruling out the sensor as the cause); or you are uncomfortable removing the back panel or handling any wiring at all — and that’s a perfectly reasonable position to take. When you call, tell the engineer: ‘My LG freezer is showing an F1 error code, which I understand relates to the freezer temperature sensor. I’ve already tried a full power reset and a manual defrost [and replaced the thermistor, if applicable], and the code has returned.’ This tells them immediately that the basic fixes have been ruled out and saves you being charged for diagnostic steps you’ve already completed. Look for engineers registered with Which? Trusted Traders or who hold City & Guilds appliance repair qualifications. LG’s own UK service line (0344 847 5454) can also book an authorised engineer if your appliance is still under warranty.
⚖️ Repair or replace?
If your LG freezer is under 7 years old, repair is almost always the right call. A thermistor replacement — whether DIY or professional — is a low-cost fix relative to the price of a new appliance. If the fault turns out to be the main control board, repair still makes financial sense for appliances up to around 8–9 years old, since LG control boards typically cost £80–£180 in parts and LG has good parts availability in the UK through suppliers like 4ourhouse and Ransom Spares. If your freezer is over 10 years old and the repair estimate exceeds £150–£200 in labour and parts, it’s worth comparing that against the cost of a new equivalent model — a mid-range LG freestanding freezer typically retails for £350–£600 in the UK. Equally, if this is the second or third fault in 18 months, recurring reliability issues are a strong signal that the appliance is nearing the end of its useful life. LG generally has good build quality and parts are not difficult to source, so a single, clearly identified fault on a mid-age appliance is rarely a reason to replace rather than repair.