BoilerFaultCodes.com
ON OFF ON High

Your boiler has tried to start up several times but failed to light the flame, causing it to shut down for safety.

Technical description: Ignition lockout error
Typical repair cost: £100-350 (including labour)

DIY fix possible

Check that your gas emergency control valve is open and you have credit on your meterPress the reset button or turn the control knob to 'O' and back to 'I'Check if other gas appliances in your home, like a hob, are working correctly

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A boiler cover plan would cover faults like ON OFF ON — no call-out fees, no surprises.

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