BoilerFaultCodesIdeal F5 Fault Code
The Ideal F5 fault code means: your boiler's internal sensor that monitors the temperature of the water coming back into the unit has developed a fault, preventing the system from operating correctly.. It appears on 12 Ideal models in our database.
Technical description: Return Thermistor Fault
What causes the Ideal F5 fault?
This fault occurs when the boiler's internal computer stops receiving a reliable signal from the sensor that monitors the temperature of the water returning from your radiators. The most common reason is that the sensor itself has worn out or suffered an electrical failure, meaning it can no longer tell the boiler if it is safe to continue heating.
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 F5 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atlantic Combi Repair: £120-220
- Concorde Repair: £120-£210
- GB24 / GB30 Repair: £120-220
- i Combi 2 Repair: £90-180
- Instinct2 24 Repair: £90-160
- Logic Air Repair: £150-250
- Logic Code Combi ESP1 Repair: £100-£180
- Logic Combi C24 C30 C35 Repair: £90-160
- Logic Combi ESP1 Repair: £90-180
- Logic Max Combi Repair: £100-£180
- Logic+ Heat H Repair: £90-180
- Logic+ System Repair: £100-180
Source
Ideal F5 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