BoilerFaultCodesIdeal E5 Fault Code
The Ideal E5 fault code means: your heat pump has stopped working because one of its outdoor temperature sensors is sending an incorrect or missing signal to the main control board.. It appears on 1 Ideal model in our database.
Technical description: Outdoor Unit, Air to Refrigerant Heat Exchanger Outlet Thermistor (T3) Error
What causes the Ideal E5 fault?
This fault occurs when the heat pump’s control board loses communication with the sensor that monitors the temperature of the coils outside. This usually happens because the sensor itself has failed internally or the electrical wiring has become corroded or loose over time. Without this specific data, the system cannot safely manage the heating process and shuts down to prevent damage.
This issue is more frequent during winter, as extreme cold and moisture can accelerate the degradation of exposed electrical sensors and wiring.
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 E5 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal E5 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