LG F16 fault codewhat it means and how to fix it
LG say a heating issue was detected. They publish F19 with word-for-word identical text, so both codes land here.
Take care
Get a qualified appliance engineer to look at your LG F16
We do not pass enquiries to a repair firm, so there is no form here. When you book a qualified appliance 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 F16 means
LG document F16 as "a heating issue was detected", requiring service, and then document F19 with exactly the same sentence. Nothing in LG’s material distinguishes the two, so pretending to know a difference would be inventing one. What both codes mean in practice is that the appliance asked for microwave power and then failed to observe the result it expected. That is a self-check rather than a component report, and it matters because it is the one code family in LG’s list that speaks directly to the complaint most owners actually arrive with: the microwave runs, the light is on, the turntable goes round, the fan is audible, and the food comes out cold.
On most brands that complaint has no code attached at all and you are left inferring it from behaviour. LG produce a code for it. Everything in the microwave generation chain is on the far side of the outer cover: the transformer or inverter that steps the mains up to a few thousand volts, the magnetron that turns that into microwaves, the waveguide that carries them into the cavity, and the thermal cut-outs watching the whole business. So is the high-voltage capacitor, which stays charged after the plug is out and is the reason this category has a different safety rule from everything else on this site.
There is genuinely nothing here for an owner to look at, and the pages that suggest otherwise are describing work that starts with removing the cover. Two things are worth doing before you book: cycle the power once, because LG ask for that on every F code and a one-off will not come back, and if the appliance has recently been run empty or with a very small item in it, say so when you call. That is the single most common way a magnetron gets shortened and it changes what an engineer expects to find.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Magnetron failed or weakened | The commonest real cause of no heat. It draws current and produces little output, so the appliance runs normally and cooks nothing. | Common |
| High-voltage transformer, diode or capacitor failed | The supply chain feeding the magnetron. Any break in it leaves a microwave that behaves perfectly and generates nothing. | Common |
| Inverter board fault on inverter models | The NeoChef range drives power electronically rather than with a mains transformer, so on those models the part behind a no-heat code may be the inverter board rather than a transformer. | Occasional |
| A thermal cut-out has opened | A protection device that interrupts the heating circuit after an over-temperature event, which reads as heating not happening. | Occasional |
| Damage from running the appliance empty | With no load the energy returns to the magnetron. It is the one thing an owner can do that reliably shortens its life. | Occasional |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£100–£220
Time on site
1h 30m
A magnetron fitted is typically £100 to £180; transformer or diode work is similar because the visit dominates. Inverter models can reach £220. Nothing here is owner-serviceable, so there is no cheap branch to this code.
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
- F11Get it checkedAn inverter communication error in LG’s words. The control board and the inverter have stopped talking, and only inverter models can show it.Related: magnetron and high voltage
- F13Get it checkedLG publish F13 as a voltage error. The same modal is titled for F14 and F15 and explains neither, so no meaning exists for those two.Related: magnetron and high voltage
- F3Get it checkedLG document this one twice and differently. One article says wipe the touch panel, the other says the control panel is faulty and needs service.Related: same brand
- LOCUsually simple to fixNot a fault. LOC is LG’s child lock, and it releases by holding STOP/CLEAR until the display drops it.Related: same brand
- DOORGet it checkedThe word DOOR rather than a number. LG say the door is not closed or the latch is not engaged, and they include transit packing as a cause.Related: same brand
- E10Get it checkedLG say an internal short was detected in the control board, and then give you something to try anyway: unplug it for a full minute.Related: same brand
Own a LG microwave? Save it and its codes come first next time.
Related guides
Common questions about LG F16
Is there really no difference between F16 and F19?
Not one that LG publish. Both entries in their code table carry identical wording. If some difference exists in their service documentation it is not in anything they make available, and inventing a distinction would be worse than saying so.
Everything looks and sounds normal. Are you sure it is not heating?
A microwave that is not generating still lights, still turns and still runs its fan, because all of that is driven separately. The test is a mug of water on full power for a minute: if it is not appreciably hotter, nothing is being generated.
Can I test the magnetron myself?
No, and this is the category where that answer is not caution for its own sake. The high-voltage capacitor holds a charge with the appliance unplugged, and every service manual we have read instructs engineers to discharge it before touching anything. The cover stays on.
Is a magnetron worth replacing?
On a built-in, usually yes, because a replacement appliance has to fit the housing. On a countertop model the part and the visit together are often close to the price of a new microwave, and an engineer will normally tell you that before starting.
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
- Manufacturer technical and service documentation
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.