BoilerFaultCodes.com
4 High

Your boiler has failed to light the burner on start-up and has safely shut down to prevent gas from flowing without a flame.

Call an engineer soon

Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: lockout (If the boiler has been turned off for some time the first attempt to light it may result in a lockout 4)
Typical repair cost £100-250 (including labour)

DIY fix possible

Locate the Reset button on the front control panel.Press and hold the reset button for 2-3 seconds.Wait for the boiler to cycle through its start-up phase; you may need to repeat this up to three times if the boiler has been off for a long period.

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