F.344 High

Vaillant F.344 Fault Code

Also written as F344 — same fault.

The Vaillant F.344 fault code means: your boiler has lost the digital settings it needs to safely control the flame, meaning it cannot operate until these are reset or the internal hardware is replaced.. It appears on 3 Vaillant models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Transmission fault for calibration values. The control electrode can no longer be used.
Typical repair cost £200-450 (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.344 fault code

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

Source

Vaillant F.344 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