BoilerFaultCodesYour boiler is having trouble managing the flame correctly and has locked itself for safety after failing to stabilise.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Ion control deviation is too big – try resetting the boiler
What causes this fault?
This fault happens when the boiler's internal sensor detects that the flame is burning inconsistently or not matching the expected safety signals. It is often caused by a worn-out sensing probe that can no longer 'see' the flame clearly, or a gas valve that is failing to deliver the correct amount of fuel to keep the burner stable.
DIY fix possible
Locate the reset button on your boiler's control panelPress and hold the reset button for at least 5 secondsWait for the boiler to attempt to restart; if the code returns immediately, call a Gas Safe engineer
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like 12-64 — 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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