Glow-worm F67 Fault Code: Causes, Fixes & Repair Costs
What does the Glow-worm F67 fault code mean?
The F67 fault code on a Glow-Worm boiler points to a problem with the main printed circuit board (PCB) — the central control unit that coordinates every component in your boiler, from the ignition sequence through to the pump, fan, and gas valve. When the PCB detects an internal fault or loses reliable communication with connected parts, it triggers a lockout and displays F67 to prevent unsafe operation. Note that F67 sits within a family of related PCB fault codes (F61–F67) on Glow-Worm boilers; while they all point broadly to the main board, each sub-code can indicate a slightly different aspect of the failure, so always tell your engineer the exact code shown on the display. Because the PCB is the brain of the boiler, this fault will typically prevent heating and hot water until the underlying issue is resolved. A Gas Safe registered engineer is required to diagnose and repair this fault — it is not suitable for DIY intervention.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Age-related PCB deterioration Common
After many years of constant heating and cooling cycles, the internal circuitry of the PCB — including capacitors, resistors, and solder joints — gradually degrades. Boilers over ten years old are particularly susceptible, and a worn board may fail entirely or produce intermittent lockouts before giving up completely.
- Cracked or dry solder joints Common
The repeated thermal expansion and contraction that occurs every time the boiler fires and cools can eventually crack the tiny solder connections on the PCB. A hairline crack can cause intermittent faults that are hard to reproduce but will worsen over time until the board fails outright.
- Water or condensation ingress Sometimes
Internal leaks from a faulty pump, heat exchanger, or pressure relief valve can allow water droplets or condensation to reach the PCB. Even a small amount of moisture is enough to cause corrosion or short circuits on the board's components.
- Wiring or connector faults Sometimes
Loose, corroded, or damaged wiring harnesses between the PCB and other components — such as the fan, thermistors, or gas valve — can mimic a PCB failure. An engineer will use a multimeter to test continuity and voltage before condemning the board, as a straightforward connector issue is far cheaper to resolve than a full replacement.
- Component miscommunication causing board overload Rare
If another part of the boiler — for example the fan or a thermistor — sends incorrect signals to the PCB, the board may interpret this as an internal fault and trigger an F67 lockout. In these cases, replacing the PCB alone will not clear the fault; the root cause component must also be identified and replaced.
How to fix it
- Reset the boiler once DIY safe
Turn the central heating control knob to the reset position (indicated by the power symbol), hold for a few seconds, then return it to your desired temperature setting. Wait a couple of minutes to see if the boiler restarts normally. Only attempt this once or twice — repeated resets without success indicate the fault needs professional attention and further resets can mask the underlying problem.
- Check for an active boiler cover or warranty DIY safe
Glow-Worm boilers are sold with a standard manufacturer warranty of up to seven years, extendable to fifteen years when the boiler is correctly installed and serviced annually by a Gas Safe engineer. Check your paperwork or contact Glow-Worm directly to see if your boiler is still covered — a PCB replacement under warranty costs you nothing.
- Check for visible signs of a water leak around the boiler DIY safe
Look around the base of the boiler casing and the pipework connections for any damp patches, drips, or limescale staining. Do not touch internal components, but if you spot an active leak, turn off the boiler and contact an engineer promptly, as ongoing moisture ingress will cause further PCB damage.
- Contact a Gas Safe registered engineer for diagnosis Gas Safe engineer
An engineer will carry out a visual inspection of the PCB for signs of burning, corrosion, or water damage, and use a multimeter to test voltages and continuity across the board and its wiring harnesses. This step is essential before any parts are ordered — a thorough diagnosis often reveals that the fault lies in a connector or a separate component rather than the PCB itself, potentially saving significant cost.
- Engineer to carry out PCB repair or replacement Gas Safe engineer
If a cracked solder joint or damaged connector is found and the rest of the board is sound, a targeted repair may restore function. Where the board is burned, corroded, or water-damaged, full replacement with a genuine Glow-Worm or quality reconditioned PCB (supplied with a warranty) is the recommended course of action. The engineer will then reset and commission the boiler to confirm the fault has cleared.
Parts you may need
- Glow-Worm PCB (main control board) · from £250
- Wiring harness / loom · from £45
- Fan assembly (if implicated in miscommunication fault) · from £120
- Flow or return thermistor · from £25
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £300–£600, depending on the underlying cause.
Frequently asked questions
Can I fix a Glow-Worm F67 fault myself?
No. The F67 code is a PCB fault and any work on the boiler's control board, wiring, or internal components must be carried out by a Gas Safe registered engineer. The only safe steps you can take at home are a single reset attempt and a visual check for external water leaks. Attempting to open the boiler casing and probe the PCB without the correct training and test equipment risks electric shock, gas escape, or further damage to an expensive component.
Is the F67 code always caused by a failed PCB, or could it be something else?
Not always. While F67 sits within Glow-Worm's PCB fault family (F61–F67), an engineer will first rule out wiring faults, corroded connectors, and rogue signals from other components such as the fan or a thermistor before concluding the board itself has failed. Misdiagnosing this and replacing the PCB when the real culprit is a £25 thermistor is a costly mistake, which is why a proper diagnostic with a multimeter is the essential first step.
How much does it cost to replace a PCB on a Glow-Worm boiler in the UK?
For most homeowners, a PCB repair or replacement on a Glow-Worm boiler typically costs between £300 and £600 including parts and labour. Minor repairs such as resoldering cracked joints tend to sit at the lower end, while a full OEM board replacement with engineer call-out and VAT can reach the higher end. In rare cases — for instance older models where the board is no longer in production — costs can exceed £700. If your boiler is still under Glow-Worm's manufacturer warranty (up to 15 years with annual servicing), the repair should be covered at no charge.
Is it worth repairing an F67 fault or should I replace the boiler?
This depends largely on the age of the boiler. If it is under ten years old and otherwise in good condition, a PCB replacement is usually worthwhile and can restore many more years of reliable service. For boilers over twelve to fifteen years old, it is worth getting a new boiler quote at the same time as the repair quote — if the repair cost is approaching half or more of a new boiler's installed price, replacement often delivers better long-term value and improved energy efficiency with a modern A-rated unit.