BoilerFaultCodesYour boiler is struggling to keep a steady flame when it is running at its lowest power setting, causing it to operate in a restricted safety mode.
This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.
Technical description: Comfort safety mode flame loss at minimum load
What causes this fault?
This fault happens when the boiler's internal sensors can no longer detect a stable flame while the unit is ticking over at its lowest power. It is usually caused by a worn-out spark probe that can't 'see' the flame anymore, or a gas valve that is no longer delivering the precise, tiny amount of fuel needed for low-level operation.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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 S.46 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.