High Lockout
F.10 on Vaillant ecoTEC

Your boiler has stopped working because one of its internal sensors has developed an electrical fault and can no longer measure 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 NTC short circuit

What causes this fault?

This fault occurs when the electrical connection within the flow temperature sensor fails, causing it to send an incorrect signal to the main control board. The most common reason is that the sensor has developed an internal short circuit due to age, or moisture has compromised the wiring connections. Because the boiler can no longer safely monitor how hot the water is, it shuts down as a safety precaution.

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.11View →F.73View →

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