This fault can involve incomplete combustion and carbon monoxide.
If anyone in the property feels sick, dizzy or drowsy, or you can smell gas: open the windows, leave the building, and do not switch anything on or off. Then call the National Gas Emergency Service.
0800 111 999Glow-worm F.62 fault codewhat it means and how to fix it
The gas valve did not shut off when told to — the flame signal lingered after the close command. Glow-worm list a delayed or leaking valve or the electronics. Switch off; call an engineer.
Stop — this needs an engineer
Get a Gas Safe registered engineer to look at your Glow-worm F.62
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
Can you smell gas?
The right answer depends on what you can see. Pick the one that matches.
Choose the option on the left that matches what your appliance is doing, and the answer for that case appears here.
Yes, at the boiler or anywhere in the house
Assume the valve is passing.
Gas off at the meter if safe, leave the property, call 0800 111 999 from outside.
No smell
Likely the sensing or the electronics, but only an engineer can prove the valve seals.
Switch the boiler off at the fused spur and book a Gas Safe registered engineer. Do not reset.
What F.62 means
F.62 is "Fault: Gas valve switch-off control" in the Glow-worm tables, and the causes are "delayed switch-off of gas valve assembly, delayed extinguishing of flame signal, gas valve assembly leaking, electronics defective". The board closed the valve at the end of a burn and expected the flame signal to vanish within a set time; it did not. The Compact manual names it "delayed shutdown of the fuel control valve" and lists the ignition electrode as a possible culprit too, because an electrode whose signal decays slowly can imitate a flame that lingers.
So one reading of F.62 is a valve that is sticking or passing — gas continuing to reach the burner after it should have stopped — and the other is a sensing fault that only looks like that. The boiler cannot distinguish them and locks out hard; so should you.
No Glow-worm user guide gives the householder any action for F.62, and this page carries none. The two-digit Ultracom2, Betacom 24a and Betacom2 boilers print F62 as "gas valve closure fault" within their main-board group, and the CI-era trade table has "16 — gas safety valve failure" as the nearest ancestor. If there is any smell of gas, the leaking-valve reading is the one to act on: gas off at the meter, out of the house, 0800 111 999.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Flame signal decaying slowly | A sooted or cracked electrode, or a damp lead, keeps reporting ionisation for a moment after the flame is gone. The Compact manual lists the ignition electrode against F.62 for this reason. | Common |
| Gas valve slow to close or passing | Glow-worm's "delayed switch-off" and "gas valve assembly leaking". Debris on the seat, a tired spring or a coil that holds after de-energising all leave a flame burning past the close command. | Occasional |
| Electronics fault | The valve driver or the flame amplifier on the PCB. Glow-worm's last cause, and the finding once the valve has been proved to seal and the electrode is clean. | Occasional |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£90–£450
Time on site
1h 30m
Electrode £90–£180. Gas valve £250–£400. PCB £250–£450.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Glow-worm ignition and flame-sensing electrode
£18–£45Authorised Glow-worm parts distributor
Price checked 28 September 2026
Glow-worm gas valve assembly
£90–£200Authorised Glow-worm parts distributor
Price checked 28 September 2026
Glow-worm main PCB
£150–£320Authorised Glow-worm parts distributor
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Glow-worm fault codes
- F.28Get it checkedThree ignition attempts have failed and the boiler has locked out. Glow-worm's guides let you check the gas supply and the condensate pipe and reset three times before calling anyone.Related: ignition and gas supply
- F1Get it checkedOn Ultracom, Flexicom and Ultrapower boilers F1 is an ignition lockout after five failed attempts, and Glow-worm's guides let you reset it. On Energy and Ultimate boilers F.01 is the return sensor instead.Related: ignition and gas supply
- F.29Get it checkedThe burner lit and then the flame went out while running. Glow-worm blame the gas supply, flue gas recirculating, earthing, the spark transformer and, on newer manuals, a blocked condensate pipe.Related: ignition and gas supply
- F.61Get it checkedThe board cannot drive the gas valve properly — a short in its wiring, coils shorted to earth, or the electronics. The valve stays shut until an engineer has traced it.Related: ignition and gas supply
- F.27Stop — call an engineerThe boiler is sensing a flame when there should not be one. Glow-worm list moisture on the electronics, a failed flame monitor or a leaking gas valve. Not a reset job.Related: ignition and gas supply
- F.68Get it checkedThe flame is burning but its signal is unstable. Glow-worm list air in the gas, low gas pressure, a wrong combustion setting or injector, a poor electrode connection or a blocked condensate pipe.Related: ignition and gas supply
Own a Glow-worm boiler? Save it and its codes come first next time.
Related guides
Common questions about Glow-worm F.62
Why not just reset and see?
Because a reset asks the board to run a burn cycle and close the valve again, and if the valve is the fault you are repeating the unsafe event. The board locked out to stop exactly that.
Is it always the gas valve?
No. Glow-worm list the flame signal and the electronics too, and the Compact manual puts the electrode on the list. But the valve is the possibility that matters until it is ruled out.
Cost?
Electrode £90–£180. Gas valve assembly £250–£400. PCB £250–£450. Plus the diagnostic time, which on this code should include a let-by test on the valve.
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 technical and service documentation
- 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.