BoilerFaultCodesYour boiler has shut down because it has either gotten too hot or it is unable to supply gas to the burner.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Overheat ’stat open/gas valve failure. Check wires/re-set ’stat. Test valve coils. Test for 230V and Neutral at PCB & plug on gas valve
What causes this fault?
This fault occurs when the boiler's internal temperature reaches a dangerously high level, triggering a safety switch to prevent damage. Alternatively, the boiler may have failed to detect the flow of gas required to maintain a flame, which is often caused by a failing gas valve or a communication error from the main control board. If the system cannot safely regulate heat or fuel, it shuts down entirely for your protection.
This fault is more frequent during the first cold snap of autumn, as components like the gas valve or pump can seize up after sitting idle throughout the summer months.
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.
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A boiler cover plan would cover faults like A04 — no call-out fees, no surprises.
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Potterton Powermax HE 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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