BoilerFaultCodesIdeal E05 Fault Code
The Ideal E05 fault code means: your boiler has detected a fault with the sensor that monitors the temperature of the water leaving the unit to heat your radiators.. It appears on 6 Ideal models in our database.
Technical description: CH flow thermistor error
What causes the Ideal E05 fault?
This fault occurs when the boiler's control board loses communication with the sensor that monitors the temperature of the water heading to your radiators. The most common reason is that the internal components of the sensor have failed due to age, or the electrical connection has become loose or corroded. Because the boiler no longer knows how hot the water is, it shuts down as a safety precaution to prevent overheating.
This fault is more common in autumn and winter when the heating is first switched back on and the sensor is subjected to rapid changes in temperature.
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 →Ideal models that show the E05 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal E05 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 27 April 2026