BoilerFaultCodesPotterton 70 neon flashing Fault Code
Also written as 70NEONFLASHING — same fault.
The Potterton 70 neon flashing fault code means: your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.. It appears on 2 Potterton models in our database.
Technical description: Overheat thermostat operated. Go to section ‘J’.
What causes the Potterton 70 neon flashing fault?
This fault occurs when the water inside the boiler exceeds a safe temperature, triggering a safety switch to cut power to the burner. The most common reasons are a failed pump that isn't moving water around the system or a blockage in the main heat exchanger caused by a buildup of sludge and debris. It can also happen if the system has become air-locked, preventing the heat from being carried away from the appliance.
This fault is frequently seen at the start of autumn when the heating is turned on for the first time after summer, as pump components can seize up during long periods of inactivity.
DIY fix possible
Check that all radiator valves are fully openEnsure the system water pressure is between 1.0 and 1.5 barTurn the selector switch to the reset position for five seconds and then back to the heating/hot water mode
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Gas Safe Register →Potterton models that show the 70 neon flashing fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton 70 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