BoilerFaultCodesIdeal FA Fault Code
The Ideal FA fault code means: your boiler has detected that the temperature sensors for the water going in and out are reporting incorrect or swapped readings, which has caused the system to shut down for safety.. It appears on 12 Ideal models in our database.
Technical description: NEGATIVE DIFFERENTIAL FLOW OR RETURN THERMISTOR FAULT
What causes the Ideal FA fault?
This fault occurs when the boiler detects that the water pipe leaving the unit is cooler than the pipe returning to it, which is physically impossible during normal operation. The most common reason is that the internal temperature sensors have failed or their wiring has become cross-connected, leading the boiler to shut down to prevent overheating. It can also be triggered by a complete lack of water circulation caused by a seized pump or a significant blockage in the system.
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 FA fault code
Click a model for the full fault code list and model-specific repair notes.
- Atlantic Combi Repair: £150-300
- Concorde Repair: £120-350
- GB24 / GB30 Repair: £120-220
- i Combi 2 Repair: £100-250
- Instinct2 24 Repair: £90-180
- Logic Code Combi ESP1 Repair: £100-220
- Logic Combi C24 C30 C35 Repair: £90-180
- Logic Combi ESP1 Repair: £120-220
- Logic Max Combi Repair: £100-220
- Logic+ Heat H Repair: £100-250
- Mexico Repair: £120-350
- Sprint Repair: £120-250
Source
Ideal FA 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