High Lockout
F.10 on Vaillant ecoTEC Pro / ecoTEC Plus

Your boiler has detected an electrical fault with the internal sensor that monitors the temperature of the water leaving the unit, causing it to shut down for safety.

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 sensor responsible for measuring the temperature of the water leaving your boiler develops an electrical short circuit. The most common reason is a component failure within the sensor itself or moisture ingress that has damaged the internal wiring. Because the boiler can no longer safely monitor how hot the water is, it shuts down to prevent overheating.

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.71View →

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