High Lockout
F16 on Vaillant ecoMAX Pro 28E

Your boiler thinks it still sees a flame even though it has commanded the burner to turn off, which is a safety concern that prevents it from restarting.

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

Flame detection fault (flame presence >5 s after burner stop)

What causes this fault?

This fault occurs when the boiler’s safety sensors continue to detect a flame for more than five seconds after the gas supply should have been cut off. The most common reason is that the gas valve hasn't closed fully or the electrode that monitors the flame has become damaged and is sending a false signal. Because this is a major safety concern, the boiler will automatically shut itself down to prevent any risk.

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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