F.02 High

Vaillant F.02 Fault Code

Also written as F02 — same fault.

The Vaillant F.02 fault code means: your boiler has lost the connection to the temperature sensor inside your hot water tank, meaning it cannot currently detect when the water needs heating.. It appears on 4 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: Interruption cylinder charging sensor
Typical repair cost £150-250 (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.02 fault code

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

Source

Vaillant F.02 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