BoilerFaultCodesIdeal FLOW/RETURN THERMISTOR FAULT Fault Code
Also written as FLOWRETURNTHERMISTORFAULT — same fault.
The Ideal FLOW/RETURN THERMISTOR FAULT fault code means: your boiler has lost the ability to accurately measure the temperature of the water circulating inside it, so it has purposefully shut down to prevent damage.. It appears on 2 Ideal models in our database.
Technical description: Check flow and return thermistors
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Ideal models that show the FLOW/RETURN THERMISTOR FAULT fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal FLOW/RETURN THERMISTOR FAULT fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026