BoilerFaultCodesPotterton E129 Fault Code
The Potterton E129 fault code means: your boiler has failed to keep its flame lit while trying to automatically adjust its settings for efficient burning.. It appears on 5 Potterton models in our database.
Technical description: Loss of flame during calibration
What causes the Potterton E129 fault?
This fault occurs when the boiler's internal computer tries to adjust the gas and air mixture to ensure it is burning fuel as efficiently as possible, but the flame goes out during the process. The most common reason is that the sensor responsible for 'seeing' the flame is dirty or worn out, or the gas valve isn't providing a steady enough flow for the boiler to complete its self-check. Because the boiler cannot guarantee a safe and efficient burn, it shuts down for safety.
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 E129 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton E129 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