BoilerFaultCodesPotterton Casting Thermistor Fault Fault Code
Also written as CASTINGTHERMISTORFAULT — same fault.
The Potterton Casting Thermistor Fault fault code means: your boiler has detected a problem with a temperature sensor on the main internal heat exchanger, causing it to shut down for safety.. It appears on 2 Potterton models in our database.
Technical description: Automatic Lockout. Thermistor reading outside of limits or difference between flow and casting thermistor readings is outside of limits.
What causes the Potterton Casting Thermistor Fault fault?
This fault occur when the sensor responsible for monitoring the temperature of the boiler's main heat exchanger sends an incorrect or out-of-range signal to the control board. The most common cause is a physical failure of the thermistor itself due to age, or potentially a loose connection in the wiring that prevents the boiler from safely monitoring internal heat levels.
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 Casting Thermistor Fault fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton Casting Thermistor Fault 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