High Lockout
Red blinking light on Grant Vortex Blue

Your boiler's safety sensor thinks there is a fire inside before it has even started, causing the system to shut down for safety.

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

Presence of a false flame signal before heat request

What causes this fault?

This fault occurs when the boiler's internal sensor detects light or a signal that looks like a fire before the burner has actually started. This is usually caused by a dirty sensor lens, a faulty control box, or a leaking fuel valve that is letting a small amount of oil onto the burner head.

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.

Find a Gas Safe engineer
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