F68 Boiler Fault Code: What It Means on Every Brand

The F68 fault code appears on 5 boiler brands — Ferroli, Glow-worm, Heatline, Saunier Duval and Vaillant — and on all of them it points to the same kind of problem. The details still differ by brand (thresholds, sub-codes, reset procedure), so use the table below to jump to the page for your boiler.

Lockout — engineer likely 5 brands use this code

Which brand is your boiler?

The brand is printed on the front casing. Tap your brand for the full causes, fixes and repair costs.

Brand	What F68 means	Severity	DIY?
FFerroli	The F68 fault code (and its lockout variant A68) indicates that the boiler's control board has failed to read or load the configuration data from the BCC (Boiler Chip Card) — a small… Full guide →	Lockout — engineer likely	No
GWGlow-worm	The F68 code appears when your Glow Worm boiler's control board detects an inconsistent or fluctuating signal from the ionisation probe — the component that confirms a stable flame is… Full guide →	Lockout — engineer likely	No
HHeatline	The F68 code appears on Heatline boilers when the PCB detects an unstable or erratic flame signal from the ionisation electrode. Full guide →	Lockout — engineer likely	No
SDSaunier Duvalshown as F.68	The F.68 fault code appears when the boiler's PCB detects that the flame signal is erratic, too weak, or otherwise behaving unexpectedly during operation. Full guide →	Lockout — engineer likely	No
VVaillantshown as F.68	The F.68 code indicates that your Vaillant boiler has detected an unstable or erratic flame signal. Full guide →	Lockout — engineer likely	No

F68 brand by brand

Ferroli F68

The F68 fault code (and its lockout variant A68) indicates that the boiler's control board has failed to read or load the configuration data from the BCC (Boiler Chip Card) — a small programmable module that stores the boiler's operational settings and parameters. In plain terms, the electronics at the heart of the boiler cannot communicate properly with this card, so the boiler refuses to run as a safety precaution. Ferroli uses two prefix formats: codes starting with 'F' are blocking faults that may clear once the underlying problem is resolved, while codes starting with 'A' indicate a full lockout that requires a manual reset before the boiler will attempt to fire again. A68 is therefore the harder lockout version of the same underlying fault. Either way, this is an electronics-level problem that sits firmly in engineer territory — there is no homeowner fix beyond a single reset attempt.

Causes, fixes & costs for Ferroli F68 → · All Ferroli codes

Glow-worm F68

The F68 code appears when your Glow Worm boiler's control board detects an inconsistent or fluctuating signal from the ionisation probe — the component that confirms a stable flame is present after ignition. Rather than risk unburned gas building up in the combustion chamber, the boiler locks itself out as a safety measure. In practice, you may notice the boiler fires up, burns for a few seconds, then cuts out, often repeating this cycle before eventually displaying F68. This code sits alongside F27 and F87 in Glow Worm's group of flame-sensing faults, all of which point to problems with how the boiler detects and confirms its burner flame.

Causes, fixes & costs for Glow-worm F68 → · All Glow-worm codes

Heatline F68

The F68 code appears on Heatline boilers when the PCB detects an unstable or erratic flame signal from the ionisation electrode. Rather than confirming a clean, steady burn, the sensor is reporting a flame that flickers or cuts in and out beyond acceptable limits. The PCB continuously monitors this signal during operation and, if it strays outside safe parameters, it will lock the boiler out and display F68 to prevent unsafe operation. In short, the boiler lit — or attempted to light — but could not maintain a reliable flame signal long enough to continue running.

Causes, fixes & costs for Heatline F68 → · All Heatline codes

Saunier Duval F.68

The F.68 fault code appears when the boiler's PCB detects that the flame signal is erratic, too weak, or otherwise behaving unexpectedly during operation. In plain terms, the control board expects to see a consistent, stable flame once the burner has ignited — if the signal it receives from the ionisation circuit doesn't match that expectation, the boiler locks out and displays F.68 as a safety precaution. Because Saunier Duval is part of the Vaillant Group and both brands share the same control architecture, the F.68 code carries exactly the same definition across Saunier Duval and Vaillant boilers. The fault can be triggered by anything that disrupts combustion quality or corrupts the electrical signal feeding back to the PCB — from a low gas supply pressure through to a failing flame-sensing electrode or moisture on the circuit board.

Causes, fixes & costs for Saunier Duval F.68 → · All Saunier Duval codes

Vaillant F.68

The F.68 code indicates that your Vaillant boiler has detected an unstable or erratic flame signal. Rather than burning steadily, the flame is flickering or the balance between gas and flame is outside acceptable limits. As a safety precaution, the boiler locks out and displays F.68. Because this fault has numerous possible root causes — ranging from gas supply issues to electronics problems — a Gas Safe registered engineer is usually needed to diagnose and resolve it properly.

Causes, fixes & costs for Vaillant F.68 → · All Vaillant codes

Frequently asked questions

Is the F68 fault code the same on every boiler?

Broadly, yes — on Ferroli, Glow-worm, Heatline, Saunier Duval and Vaillant the F68 code points to the same class of fault, and the recommended response is similar. Model-specific details such as sub-codes and reset procedures still vary, so follow the page for your own brand.

Can I fix a F68 fault myself?

Not usually. On every brand listed, F68 points to a fault that needs a suitably registered engineer to diagnose and repair. A single reset to rule out a transient glitch is reasonable; repeated resets are not.

Who should I call about a F68 fault?

For gas boilers, a Gas Safe registered engineer — it is a legal requirement for any work on the appliance. If you smell gas at any point, leave the property and call the National Gas Emergency line on 0800 111 999.

General guidance only — not a substitute for professional advice, and not certified by a registered engineer. Any work on a gas appliance must be carried out by a Gas Safe registered engineer. If you smell gas, call 0800 111 999.