BoilerFaultCodesPotterton 40° neon flashing Fault Code
Also written as 40NEONFLASHING — same fault.
The Potterton 40° neon flashing fault code means: your boiler has detected a problem with the sensor that measures hot water temperature, which means your taps may not get warm.. It appears on 3 Potterton models in our database.
Technical description: Domestic hot water temperature sensor (NTC) fault
What causes the Potterton 40° neon flashing fault?
This fault occurs when the small sensor responsible for monitoring your tap water temperature fails or sends an incorrect electronic signal to the control board. The most common reason is that the internal components of the sensor have degraded over time or developed a small mineral build-up, preventing it from accurately reading how hot the water is.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Potterton models that show the 40° neon flashing fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton 40° 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