High Lockout
S.6 on Vaillant ecoTEC 65kW

Your boiler's fan is staying on for too long or running when it should be finished, preventing the next heating cycle from starting safely.

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

Heating mode – fan overrun error

What causes this fault?

This fault occurs when the boiler's control system detects that the fan is still spinning even after it was told to stop. The most common reason is a communication error between the main circuit board and the fan, or a physical fault within the fan motor itself that prevents it from shutting down correctly. Because the fan is a safety-critical component, the boiler pauses operation to prevent an unsafe mixture of gas and air.

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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