BoilerFaultCodesPotterton A.(6) Fault Code
Also written as A6 — same fault.
The Potterton A.(6) fault code means: your boiler is unable to start its pilot flame or has shut down to prevent the system from getting too hot.. It appears on 3 Potterton models in our database.
Technical description: Pilot fails to light - Overheat thermostat not operating.
What causes the Potterton A.(6) fault?
This fault occurs when the boiler's internal safety sensors detect that the unit has become dangerously hot or when the pilot light fails to stay lit. The most common reason is a failing thermocouple that can no longer sense the flame, or a tripped overheat thermostat caused by a circulation issue like a pump failure.
This issue is more common during the first cold spell of autumn, as pump blockages or airlocks often occur after the heating has been switched off all summer.
DIY fix possible
Locate the overheat thermostat reset button, usually hidden under a small plastic cap on the front or bottom panel.Press the reset button firmly until you hear a click.Attempt to relight the pilot light following the instructions on the boiler's internal door.
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Gas Safe Register →Potterton models that show the A.(6) fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton A.(6) 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