High Lockout
F.10 on Vaillant ecoMAX 828E

Your boiler has stopped working because a sensor that monitors water temperature has developed an electrical fault.

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

Short circuit – flow–NTC (< 130 °C) | Cause: NTC– plug shorted to casing, NTC defective

What causes this fault?

This fault occurs when the boiler's control board receives an incorrect electrical signal from the sensor that monitors the temperature of the water leaving the unit. The most common reason is that the sensor has failed internally or the protective coating on the connecting wires has worn away, causing an electrical short circuit. When the boiler can no longer accurately track the water temperature, it shuts down immediately 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.00View →F.11View →

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