High Lockout
F.00 / F.0 on Vaillant ecoTEC Pro / ecoTEC Plus

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.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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 this 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.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F.10View →F.11View →

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