BoilerFaultCodesPotterton Section M (Neon Flashing) Fault Code
Also written as SECTIONMNEONFLASHING — same fault.
The Potterton Section M (Neon Flashing) fault code means: your boiler has switched itself off because it has detected that the exhaust gases have become too hot, which is a safety protection measure.. It appears on 1 Potterton model in our database.
Technical description: Flue overheat thermostat may have operated. Press the reset button on the flue overheat thermostat.
What causes the Potterton Section M (Neon Flashing) fault?
This fault occurs when the internal temperature of the exhaust gases reaches a level that could damage the boiler's components or the flue system. The most common reasons for this are a build-up of limescale or sludge inside the main heat exchanger, which prevents heat from transferring to the water, or a fault with the fan and air pressure system. Because the heat has nowhere to go, it builds up until a safety sensor triggers an immediate shutdown.
This fault is more common during the winter months when the boiler is running at maximum capacity for long periods to meet higher heating demands.
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 Section M (Neon Flashing) fault code
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Source
Potterton Section M (Neon Flashing) 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