Glow-worm F.61 fault codewhat it means and how to fix it
A fault in the gas valve control circuit on the main board. The appliance will not fire and this needs an engineer.
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What F.61 means
F.61 on a Glow-worm is a gas valve control system fault, and it is a direct counterpart of the Vaillant code of the same number, which is unsurprising given the shared Vaillant Group engineering. The fault is electrical rather than mechanical: it concerns the circuit that operates the gas valve rather than gas flow itself. Vaillant Group documentation attributes it to a short circuit or earth leak in the cable harness running to the gas valve, an earth leak from the valve coils themselves, or a defective control board. All three are testable with a multimeter before anyone commits to a part, which matters because a gas valve is among the dearer components on a domestic boiler while a chafed harness produces an identical code for a fraction of the cost. Some Glow-worm literature groups F.61 with F.62 through F.67 as main board faults generally, so it is worth asking an engineer to confirm which specific circuit is at fault rather than accepting a board replacement on the strength of the code alone.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| A board fault rather than a valve fault | Worth listing first on a Glow-worm precisely because the range literature lumps F.61 in with F.62 through F.67 as mainboard conditions. On some appliances that grouping is accurate and the valve is blameless. | Common |
| Earth leakage from the valve coils | The alternative reading, inherited from the Vaillant Group definition of the same number. Confirmed by measuring coil resistance to earth, not by elimination. | Common |
| Damaged wiring between board and valve | The cheapest outcome by a wide margin. Glow-worm cases are compact and a lead resting against a hot bracket will break down eventually. | Occasional |
| Water ingress across the low-voltage side | A weeping automatic air vent above the board is a recognised way to produce electrical faults that read as component failures. | Rare |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£120–£480
A harness repair is a call-out charge of £90 to £160. A gas valve is £280 to £420 fitted. A main board is £320 to £520.
Typical UK prices including parts and labour, updated August 2026. Your quote may differ.
What other owners found
Nobody has shared what worked for them on this code yet. If you have had it, you would be the first — and it genuinely helps the next person.
Related Glow-worm fault codes
- F.28Get it checkedIgnition was unsuccessful at start-up and the boiler has locked out. Check the gas and the condensate pipe before calling anyone.Related: ignition and gas supply
- F1Stop — call an engineerNo flame was detected during ignition, so the boiler has shut the gas off and locked out. Two resets at most before calling someone.Related: ignition and gas supply
- F.29Get it checkedThe flame was established and then lost, and re-ignition failed. Different from F.28 and it points somewhere else.Related: ignition and gas supply
- EA 227Stop — call an engineerThe boiler tried to light and never detected a flame, so it has shut the gas off and locked out. This is the most common Worcester fault code.Related: ignition and gas supply
- E01Get it checkedThe appliance tried to light and could not confirm a flame, so it has locked out. In winter a frozen condensate pipe is the most likely reason.Related: ignition and gas supply
- F.28Stop — call an engineerThe boiler tried to light and failed three times in a row, so it has shut the gas off and locked out. Do not keep resetting it.Related: ignition and gas supply
Related guides
Common questions about Glow-worm F.61
One site says gas valve, another says main board. Which is it on my boiler?
Genuinely both, depending on the range. Glow-worm publish range-specific tables where F.61 through F.67 are described collectively as mainboard faults, while the underlying Vaillant Group definition of F.61 is the gas valve control circuit. Get the engineer to name the component they have tested rather than accepting either label on the strength of the number.
What should I ask for so I do not pay twice?
Ask for the result of two specific measurements: the resistance of the gas valve coils to earth, and continuity along the harness between board and valve. Those two readings decide between a harness repair, a valve, and a board, and any engineer who has diagnosed it properly will have them to hand.
Is a Glow-worm mainboard worth replacing?
On an Energy or Ultimate still inside ten years, usually yes. On an older Betacom or Flexicom, get the figure and compare it honestly against a replacement appliance, because a board is the single dearest part and the rest of the boiler is the same age as it.
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
- Interviews with working engineers
Checked by Technical reviewer (Gas Safe registration to be displayed on appointment) on 5 August 2026.