BoilerFaultCodesPotterton E33 Fault Code
The Potterton E33 fault code means: your boiler has detected an issue with the sensor that monitors the temperature of the exhaust fumes, causing the system to shut down for safety.. It appears on 1 Potterton model in our database.
Technical description: Flue thermistor error
What causes the Potterton E33 fault?
This fault occurs when the boiler's internal computer receives an incorrect or missing signal from the sensor that monitors the heat of the exhaust gases. It is usually caused by the sensor itself failing due to age, or a fault in the wiring that connects the sensor to the main control panel. Because the boiler cannot confirm that the exhaust fumes are at a safe temperature, it shuts down immediately to prevent heat damage.
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 E33 fault code
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Source
Potterton E33 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