Saunier Duval F.67 Fault Code: Causes, Fixes & Repair Costs
What does the Saunier Duval F.67 fault code mean?
The F.67 fault code appears on Saunier Duval boilers when the main PCB (printed circuit board) is not receiving a valid flame signal during or after the ignition sequence. In straightforward terms, the boiler attempts to light, but its control board either sees no flame signal at all, or the signal it receives is too weak or erratic to confirm a stable flame is present. As a safety response, the boiler locks out to prevent unburned gas from building up. Saunier Duval shares its boiler platform and fault-code architecture with Vaillant (both are part of the same group), so F.67 carries an identical meaning on Vaillant appliances. The most common culprits are a faulty ionisation (flame-sensing) electrode and PCB-related issues such as loose connections, water ingress, or a damaged board. A professional diagnosis is always needed because the fault sits squarely within the electrical and gas-detection side of the appliance.
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
- Faulty or contaminated ionisation electrode Common
The ionisation electrode sits inside the burner and generates a tiny electrical current through the flame to confirm combustion. If the ceramic body is cracked, the rod is coated with soot or oxidation, or the connecting cable has damaged insulation, the signal reaching the PCB will be absent or unreliable. This is the single most frequent cause of F.67 on Saunier Duval boilers and should be the first component an engineer inspects.
- Loose or corroded wiring and PCB connections Common
Boiler internals are subject to constant low-level vibration from the pump and fan, and over several years this can gradually work plug-and-socket connections loose on the PCB. Corrosion from humidity inside the casing can compound the problem. A poor connection between the electrode cable and the board can mimic a complete electrode failure, so an engineer will check all relevant connectors before condemning any part.
- Water ingress or condensation on the PCB Sometimes
Even a small amount of moisture on the circuit board can cause localised short circuits that damage the tracks responsible for processing the flame signal. Internal leaks — from a heat exchanger, pump seal, or pipe joint — are a well-known route for water to reach the PCB. An engineer will check for active leaks and must resolve any before assessing or replacing the board.
- Failed or cracked main PCB Sometimes
If the flame-detection circuitry on the PCB itself has failed — due to age, a power surge, or heat damage — the board will not correctly interpret even a good signal from a healthy electrode. A cracked PCB can produce identical symptoms to an electrode fault. Engineers use continuity and signal testing to distinguish between the two before recommending a board replacement.
- Mains supply voltage irregularity Rare
The PCB requires a stable mains supply to operate correctly. Persistent overvoltage or significant voltage fluctuations can interfere with the flame-detection circuit or cause cumulative damage to the board. A clue that mains voltage may be the issue is if other appliances in the property are regularly blowing fuses or tripping the RCD around the same time as boiler faults occur.
How to fix it
- Check the boiler's gas supply is live DIY safe
Before anything else, confirm that the gas isolation valve on the supply pipe to the boiler is fully open (handle parallel to the pipe). Check that other gas appliances in the property — hob, cooker, gas fire — are working normally. If there is no gas at other appliances, contact your gas supplier rather than a boiler engineer.
- Attempt a single reset DIY safe
Press and hold the reset button on the boiler's control panel as described in your user manual (typically 3–5 seconds). Allow the boiler a full minute to attempt re-ignition. If the F.67 code reappears promptly, do not keep resetting repeatedly — doing so without resolving the root cause will not help and can mask useful diagnostic information. Limit yourself to two or three resets at most.
- Engineer: inspect and test the ionisation electrode and its cable Gas Safe engineer
A Gas Safe engineer will remove the boiler casing and access the burner assembly. They will visually inspect the electrode for cracks in the ceramic insulator, check the rod for heavy oxidation or soot deposits, and test the connecting cable for continuity and insulation integrity. A lightly soiled electrode may be cleaned with fine abrasive; a cracked or failed one must be replaced with the correct Saunier Duval part.
- Engineer: check all PCB wiring connectors and grounding Gas Safe engineer
The engineer will reseat all relevant plug connectors at the PCB, paying particular attention to the flame-detection circuit. They will also verify that the electrode's ground path back to the burner chassis is intact — poor grounding can prevent a valid ionisation current even when the electrode itself is in good condition.
- Engineer: inspect for internal water leaks before touching the PCB Gas Safe engineer
Before any PCB assessment, the engineer should check around the heat exchanger, pump, and pipework joints for signs of moisture or dried limescale deposits that indicate a previous leak. Any active leak must be repaired first; fitting a new PCB into a leaking boiler risks immediate repeat damage.
- Engineer: test and replace the PCB if required Gas Safe engineer
If the electrode, cabling, and connections all test satisfactory, the engineer will assess the PCB itself — checking for visible damage such as burned tracks or cracked solder joints. If the flame-detection circuit has failed, the board will need to be replaced with a compatible Saunier Duval PCB. This is a specialist task requiring the correct part and post-installation testing of all safety functions.
- Call a Gas Safe registered engineer if the fault persists or you are unsure Gas Safe engineer
F.67 is not a fault that resolves itself or one that a homeowner can safely work on. If the reset has not cleared it, or it returns after clearing, book a Gas Safe registered engineer as soon as possible. You can verify an engineer's registration at gassaferegister.co.uk. Continuing to use a boiler that is locking out on a flame-detection fault is not safe.
Parts you may need
- Ionisation / flame-sensing electrode · from £25
- Electrode connecting cable and insulation · from £18
- Main PCB (control board) — Saunier Duval compatible · from £220
- Ignition lead set · from £30
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 £120–£400, depending on the underlying cause.
Frequently asked questions
Can I fix the Saunier Duval F.67 myself?
Not safely, no. The F.67 fault involves the boiler's flame-detection circuitry and requires access to the internal components of a gas appliance. In the UK, working inside a boiler is legally restricted to Gas Safe registered engineers. What you can safely do is check that the gas supply is on and try resetting the boiler once or twice. If the fault persists, you need to call a qualified engineer.
Will replacing the PCB definitely fix F.67?
Not necessarily — and that is exactly why a proper diagnosis matters. The PCB is one possible cause, but a faulty ionisation electrode or a simple loose connector is statistically more likely and far cheaper to fix. A good engineer will work through the electrode, cabling, and connections before recommending a board replacement. If the PCB does turn out to be the problem, expect to pay in the region of £300–£550 including labour. On a boiler older than ten years, it is worth comparing that cost against a new boiler installation before committing.
How long does it take to repair an F.67 fault?
If the problem is a dirty or failed electrode or a loose connection, an engineer can usually diagnose and resolve it within an hour or two on the same visit, provided they carry common parts. A PCB replacement takes longer — typically two to three hours — and may require the engineer to order the specific board if they do not have one on the van, which can mean a return visit.
Why does F.67 keep coming back after I reset the boiler?
A reset simply clears the fault flag and lets the boiler attempt ignition again; it does nothing to address the underlying problem. If F.67 returns each time, it means the root cause — most likely a degraded ionisation electrode, a damaged PCB connection, or water damage to the board — is still present. Repeated resets without a repair can also mask diagnostic patterns that help an engineer pinpoint the fault quickly, so it is best to stop resetting and book an engineer promptly.