F.044 Emergency

Vaillant F.044 Fault Code

Also written as F044 — same fault.

The Vaillant F.044 fault code means: your boiler is struggling to breathe properly because exhaust fumes are being trapped or pulled back into the system, preventing it from burning fuel safely.. It appears on 3 Vaillant models in our database.

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description: Fault in the flue gas route caused by recirculation or flue gas blockage. The ionisation signal for the control electrode is too low. The drift adaptation has failed.
Typical repair cost £150-350 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Vaillant models that show the F.044 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Vaillant F.044 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026