LG FU fault codewhat it means and how to fix it
The freezer did not get cold enough in the time allowed. LG give real owner steps for this one, including a paper test for the door seals.
Take care
What FU means
FU is a cycle error, and LG explain the measurement behind it: after ten minutes of starting the appliance the temperature in the freezer has not dropped below 3.5 degrees, or during operation the temperature has risen above 3.5 degrees. So the appliance set itself a target, watched the clock, and reported that it did not get there. This is one of only two codes where LG's master fault list itself breaks its own blanket request-service instruction and publishes owner steps (their separate per-code articles add resets for several others), which tells you they consider it frequently fixable without a visit.
Their sequence starts with power quality, and the detail is worth following exactly: unplug, wait sixty seconds, and plug back into a direct socket, which LG specify as without power strips or multiple sockets. A fridge on an extension lead shared with other appliances can see a voltage drop that affects the compressor, and it is a genuinely common installation shortcut in British kitchens. From there their checks are about load and airflow rather than parts. Is the compressor actually running and are the temperatures normal now. Is the freezer set to minus eighteen. How often is the door being opened. Is food blocking the vents where cold air comes in. And do the door seals actually seal, for which LG publish a test that works on any appliance and takes ten seconds: open the door, put a piece of paper between the door and the cabinet, close the door, and try to pull the paper out — it should resist if the seal is effective.
Run that test at several points around the door rather than once, because a seal usually fails in one place, typically at a corner or along the hinge side where the door has dropped. What none of this covers is the case where everything checks out and the freezer still cannot reach temperature. At that point the code is reporting the cooling system rather than the conditions around it, and it is a service call.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| A door seal that is no longer sealing | The commonest fixable cause. Warm air leaking in continuously means the freezer never reaches its target, and LG publish a paper test to find it. | Common |
| Food blocking the air vents | LG list it among their checks. Packing the freezer to the back wall stops the cold air circulating, so the sensor reads warm even though the system is working. | Common |
| Power supply problems | LG’s first step is plugging into a direct socket without power strips or multiple sockets, which suggests they see this often enough to lead with it. | Occasional |
| The door being opened very frequently | Another of LG’s named checks. Each opening admits warm damp air, and a busy household with a chest-full freezer can genuinely defeat the pull-down time. | Occasional |
| A cooling system fault | The case where all the checks pass and the freezer still will not reach temperature. That is a compressor, a fan or a charge problem and needs an engineer. | Occasional |
What to try yourself
Unplug the appliance, wait sixty seconds, and plug it back into a wall socket directly. LG specify without power strips or multiple sockets, and it is their first step for a reason.
Check the freezer is set to minus eighteen degrees. A setting that has been nudged warmer will produce this code with nothing wrong.
Look at whether food is packed against the vents at the back of the compartment, and pull it forward so air can move.
Test the door seal with a piece of paper. Shut the door on it and try to pull it out — it should resist. Repeat at several points round the door, because seals usually fail in one place.
Give it several hours after any of this before judging. A freezer that has been warm takes a long time to pull back down, and ten minutes tells you nothing.
If the seals are good, the vents are clear and it still will not reach temperature, book an engineer. At that point the code is about the cooling system.
Get a qualified refrigeration engineer to look at your LG FU
We do not pass enquiries to a repair firm, so there is no form here. When you book a qualified refrigeration engineer, tell them the make, the model and the exact code or message on the display, and ask whether they carry parts for this make — that is what turns one visit into a repair rather than a quote.
What it costs to fix
Typical repair cost
£0–£240
Time on site
1 hour
Nothing if it is a setting, the load or the socket. A door seal is a modest part; a compressor or sealed system fault usually means replacing the appliance.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Own this appliance and had this code? . Nothing is published until a person has read it.
Related LG fault codes
- OFFGet it checkedShop mode. LG publish how it gets switched on by accident at home, and give two ways out — including a ten second power cycle that does work on LG.Related: same brand
- FFGet it checkedFreezer fan. LG’s master list says request service, but their own dedicated article gives owner steps, and the usual cause is frost around the motor.Related: same brand
- dHGet it checkedThe defrost cycle ran and the temperature did not rise. LG give the exact test it failed, and their own per-code articles give a reset and a long manual defrost before the service call.Related: same brand
- Beeping with the door closedUsually simple to fixLG publish seven causes and a door switch test you can do with a finger. The fridge thinks a door is open, and usually something is holding it.Related: same brand
- CHGet it checkedLG’s master list calls this a refrigerant leak. Their per-code article is more careful: a cooling-power inspection code that can be temporary in use, with a five minute reset before the service call.Related: same brand
- LoUsually simple to fixNot a fault. LG classify this as a warning that the room is below minus ten degrees, which is why garage fridges misbehave in winter.Related: same brand
Own a LG fridge or freezer? Save it and its codes come first next time.
Related guides
Common questions about LG FU
Why does LG care what socket it is plugged into?
Because a compressor drawing its starting current through a shared extension lead can see enough voltage drop to affect how it runs. LG make it their first step — plug into a direct socket without power strips or multiple sockets — which suggests it is a frequent enough cause to lead with.
How do I test the door seal properly?
LG’s method: open the door, insert a piece of paper between the door and the cabinet, close the door, then try to pull the paper out. It should resist if the seal is effective. Do it at several points round the door rather than once, because a gasket usually fails at one corner or along the hinge side rather than all over.
The freezer feels cold. Why is it complaining?
Cold to a hand is nowhere near minus eighteen. The measurement behind this code is specific — the freezer failing to get below 3.5 degrees in the time allowed, or rising above it during operation — and a compartment that feels cold can be well above the temperature frozen food needs.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer support portal
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.