F.00 / F.0 High

Vaillant F.00 / F.0 Fault Code

Also written as F00F0 — same fault.

The Vaillant F.00 / F.0 fault code means: your boiler has stopped working because it can no longer communicate with the internal sensor that monitors the temperature of the water leaving the unit.. 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: Flow temperature sensor interruption

What causes the Vaillant F.00 / F.0 fault?

This fault occurs because the connection between the boiler's main control board and the temperature sensor has been broken. The most common reason is that the sensor itself has suffered an internal failure or the electrical wiring connecting it has become loose or corroded over time.

Typical repair cost £90-160 (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.00 / F.0 fault code

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

Source

Vaillant F.00 / F.0 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 27 April 2026