BoilerFaultCodesYour boiler's flame sensor is detecting an unusual reading that is outside of its normal operating range, which has caused the system to stop as a safety precaution.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Ion base value exceeds the upper factory limit – try resetting the boiler
What causes this fault?
This fault occurs when the boiler's internal sensors detect an electrical current that is too high or unstable during the combustion process. It is often caused by a buildup of carbon on the flame-sensing probe or a fault in the wiring that prevents the control board from accurately monitoring the burner. As a safety measure, the boiler shuts down because it cannot be certain that the flame is burning correctly or safely.
DIY fix possible
Locate the reset button on the boiler control panelPress and hold the reset button for 2-3 secondsWait for the boiler to complete its restart sequence and check if the code clears
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A boiler cover plan would cover faults like 12-67 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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