BoilerFaultCodesPotterton A04 Fault Code
The Potterton A04 fault code means: your boiler has shut down because it has either gotten too hot or it is unable to supply gas to the burner.. It appears on 1 Potterton model in our database.
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 the Potterton A04 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.
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Gas Safe Register →Potterton models that show the A04 fault code
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Source
Potterton A04 fault code information on this page is sourced and cross-checked against the official Potterton service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026