High Lockout
Slow flash on Worcester Bosch Greenstar Si

Your boiler has detected a safety-related issue and has locked itself out to prevent further damage, requiring a manual reset to restart.

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

Occurs once per second. Can only be cleared by using the facia reset button (press for at least one second).

What causes this fault?

This fault occurs when the boiler fails to detect a stable flame after several attempts to light. The most common reasons include a lack of gas supply, worn-out ignition parts that can no longer create a spark, or a sensor that is too dirty to 'see' the flame even when it is present.

This fault is more common in winter, as severe cold can cause external gas regulators to freeze or pipes to become blocked, disrupting the fuel flow required for ignition.

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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