F92 Boiler Fault Code: What It Means on Every Brand

The F92 fault code appears on 2 boiler brands — Glow-worm 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 2 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 F92 means	Severity	DIY?
GWGlow-worm	The F92 (sometimes displayed as F.92) fault code appears on Glow-Worm boilers that share the Vaillant ecoTEC-derived platform — typically newer or higher-specification models. Full guide →	Lockout — engineer likely	No
VVaillantshown as F.92	The F.92 code on a Vaillant boiler signals a gas group configuration mismatch. Full guide →	Lockout — engineer likely	No

F92 brand by brand

Glow-worm F92

The F92 (sometimes displayed as F.92) fault code appears on Glow-Worm boilers that share the Vaillant ecoTEC-derived platform — typically newer or higher-specification models. It signals that the boiler's control board has detected a mismatch between the combustion quality and the gas group it has been configured for. In practical terms, the PCB's coding resistor setting does not align with the gas type being supplied, or the combustion parameters have drifted outside the acceptable range. Because this represents a potential unsafe combustion condition, the boiler locks out automatically as a safety measure. Note that this code does not appear on all Glow-Worm ranges — older Betacom, Flexicom, and Energy series models use a different fault-code set — but if your display is showing F92 or F.92, this page covers everything you need to know.

Causes, fixes & costs for Glow-worm F92 → · All Glow-worm codes

Vaillant F.92

The F.92 code on a Vaillant boiler signals a gas group configuration mismatch. In practical terms, the coding resistor fitted to the PCB does not correspond to the gas family that has been entered into the boiler's settings — or the gas family check was not completed correctly during commissioning. Because the boiler cannot confirm it is configured for the correct gas type, it locks out as a safety precaution. This fault is almost always rooted in a commissioning or configuration error rather than a mechanical failure, making it a job for a Gas Safe registered engineer rather than a component replacement.

Causes, fixes & costs for Vaillant F.92 → · All Vaillant codes

Frequently asked questions

Is the F92 fault code the same on every boiler?

Broadly, yes — on Glow-worm and Vaillant the F92 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 F92 fault myself?

Not usually. On every brand listed, F92 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 F92 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.