BoilerFaultCodesPotterton A.(2) Fault Code
Also written as A2 — same fault.
The Potterton A.(2) fault code means: your boiler's small pilot flame is not staying lit, which is preventing the main burner from starting up to provide heat.. It appears on 3 Potterton models in our database.
Technical description: Pilot fails to light - Control knob not pressed fully down.
What causes the Potterton A.(2) fault?
This fault occurs when the small flame responsible for lighting the main burner fails to stay lit or cannot be detected by the system. The most common reasons include a worn-out heat sensor called a thermocouple, a blocked pilot hole preventing gas flow, or a buildup of soot on the sparking component. Without this steady pilot flame, the boiler shuts down as a safety precaution to prevent unburnt gas from escaping.
This issue is more frequent in autumn when boilers are turned back on after being idle all summer, as dust and debris often settle in the pilot assembly during the warmer months.
DIY fix possible
Locate the grey or white control knob on the boiler gas valve.Turn the knob to the 'Pilot' or 'Star' position and press it down firmly and completely.While holding the knob down, press the igniter button repeatedly until the pilot flame appears.Continue to hold the control knob down for 20-30 seconds after the flame is lit before slowly releasing it.
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Gas Safe Register →Potterton models that show the A.(2) fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton A.(2) 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