High Lockout
S.6 on Vaillant ecoTEC exclusive

Your boiler has paused its operation because it is not receiving the correct feedback signal from the fan that pushes exhaust gases out of the system.

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

Fan return flow

What causes this fault?

This fault occurs when the boiler's control board sends a command to the fan but does not receive the expected signal back to confirm it is spinning at the right speed. It is often caused by a mechanical failure within the fan motor or a communication breakdown in the electrical wiring between the fan and the main computer. Without this confirmation, the boiler stops for safety to ensure harmful exhaust gases are being correctly removed.

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.32View →S.32View →

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