High
F.11 on Vaillant aquaPLUS

Your boiler has detected an electrical fault with the sensor that monitors water returning from your radiators, often caused by a faulty part or damaged wiring.

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 - return-NTC (<130 °C) | NTC-plug shorted to casing, NTC defective

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 →

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