BoilerFaultCodesPotterton A.(1) Fault Code
Also written as A1 — same fault.
The Potterton A.(1) fault code means: your boiler is unable to start because it cannot light the small pilot flame, meaning you will have no heating or hot water.. It appears on 3 Potterton models in our database.
Technical description: Pilot fails to light - No gas supply.
What causes the Potterton A.(1) fault?
This fault occurs when the boiler attempts to start up but the small pilot flame fails to ignite or stay lit. The most common reasons include a blocked pilot burner caused by dust buildup, a worn-out sensor that can no longer detect the flame, or a fault within the gas valve preventing fuel from reaching the burner.
This issue is frequently seen after the boiler has been switched off all summer, as debris or air can settle in the pilot assembly during periods of inactivity.
DIY fix possible
Check that your home's main gas emergency control valve is in the 'on' position.Verify if other gas appliances, like a cooker or hob, are working to confirm gas supply.If you have a prepaid gas meter, ensure you have sufficient credit and the meter hasn't locked out.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Potterton models that show the A.(1) fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton A.(1) 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