BoilerFaultCodesYour boiler has lost its memory regarding the type of gas it uses and needs to be reconfigured by a professional to operate safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: No setting for the type of gas is stored | Set gas type in PCB (see page 30)
What causes this fault?
This fault occurs when the boiler's internal computer suffers a data loss and can no longer identify which fuel source it should be burning. The most common reason is that the main control board has developed an electrical defect or has been replaced without the necessary configuration codes being entered. Without this specific profile, the boiler will not fire up because it cannot guarantee a safe combustion process.
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 F.41 — no call-out fees, no surprises.
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Vaillant Thermocompact is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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