BoilerFaultCodesIdeal F5 Fault Code
The Ideal F5 fault code means: your boiler has lost its ability to monitor the temperature of the water returning from your radiators, often causing it to shut down to prevent damage.. It appears on 17 Ideal models in our database.
Technical description: Return thermistor fault
What causes the Ideal F5 fault?
This fault occurs when the sensor responsible for measuring the temperature of the water entering the boiler from your heating system fails or sends an incorrect signal. The most common reason is that the internal component has simply worn out over time, though it can also be triggered by loose electrical connections or moisture damage to the sensor. To protect the boiler from overheating, the system stops firing because it can no longer safely monitor the internal water 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 F5 fault code
Click a model for the full fault code list and model-specific repair notes.
- Compact Repair: £100-£180
- Compact HE Repair: £90-160
- Concorde Repair: £120-£210
- Esprit Repair: £90-180
- Logic Code Combi ESP1 Repair: £100-£180
- Logic Combi C24 C30 C35 Repair: £90-160
- Logic Combi ESP1 Repair: £90-180
- Logic Max & Logic Plus Repair: £90-180
- Logic Max Combi Repair: £100-£180
- Logic Max Plus Repair: £90-180
- Logic Max System Repair: £100-£180
- Logic+ Repair: £90-180
- Logic+ Heat Repair: £90-180
- Logic+ System Repair: £100-180
- Mexico Repair: £120-£200
- Sprint Repair: £90-180
- Vogue Repair: £90-180
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 27 April 2026