High Lockout
F.64 on Vaillant Turbomax Plus VUW 242EH

Your boiler has stopped working because its internal computer is receiving conflicting or faulty information from its temperature sensors.

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

Sensor or electronics fault | Check NTC's/connections or electronics defect

What causes this fault?

This fault occurs when the boiler's main control board detects a logic error between the heat sensors on the flow and return pipes. It usually happens because one sensor is sending a reading that is physically impossible or because the electrical signals are being interrupted by a faulty circuit board.

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.61View →F.62View →F.63View →F.65View →F.67View →

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