Ideal FA Fault Code: Causes, Fixes & Repair Costs
What does the Ideal FA fault code mean?
The FA fault code on Ideal boilers indicates that the boiler has detected a reversed flow and return condition. In a correctly plumbed system, hot water leaves the boiler via the flow pipe and returns to be reheated via the return pipe. When the boiler's sensors detect that water temperatures suggest these are the wrong way round — most often because the circulation pump is pushing water in the wrong direction — the PCB triggers a safety lockout and displays FA. The boiler will not fire until the underlying problem is identified and corrected, and the fault is manually cleared.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Circulation pump installed incorrectly Common
The most common reason for an FA code is a pump that has been fitted the wrong way around, typically after a recent service or pump replacement. Every pump has a directional arrow on its body indicating the intended flow direction. If this arrow points against the boiler's flow pipe, the pump pushes water in the wrong direction, immediately triggering FA. The pump head label should also be upright when correctly oriented.
- Circulation pump not running or seized Common
If the pump has seized, lost power, or stopped running for any reason, there will be no proper water movement through the system. The boiler's flow and return temperature sensors can interpret this stagnation as a reversed flow condition and lock out with FA. You may notice the pump is neither warm nor vibrating slightly when the boiler tries to fire.
- Closed isolation valves or radiator valves Sometimes
If isolation valves beneath the boiler or radiator valves around the system are partially or fully closed, circulation is restricted or blocked. This can cause abnormal temperature differentials across the flow and return sensors that the PCB interprets as a reversed flow. Ensuring all valves are fully open is a straightforward check before calling an engineer.
- Air lock in the system Sometimes
A significant air lock in the pipework or heat exchanger can prevent water circulating freely, again creating temperature sensor readings consistent with a reversed flow. This is more likely after draining work, a recent power flush, or if system pressure has been very low for an extended period.
- Wiring fault or PCB issue Rare
In rarer cases, a wiring fault on the pump circuit or a failing PCB can cause incorrect sensor readings or prevent the pump from receiving its run signal, producing a spurious FA code even when the physical pipework and pump are correctly installed.
How to fix it
- Check all isolation valves and radiator valves are fully open DIY safe
Locate the isolation valves underneath the boiler (usually small lever or slotted valves on the incoming and outgoing pipes) and confirm they are fully open — levers in line with the pipe, screwdriver slots horizontal. Walk around the property and make sure all thermostatic and lockshield radiator valves are turned fully open. A closed valve anywhere in the circuit can restrict circulation enough to trigger FA.
- Verify system pressure is within the normal range DIY safe
Check the pressure gauge on the boiler — it should read between 1.0 and 1.5 bar when the system is cold. If it is below 0.8 bar, top it up using the filling loop (refer to your boiler manual for the location of the filling loop on your specific model). Very low pressure means insufficient water in the system for normal circulation, which can contribute to sensor faults.
- Attempt a single boiler reset DIY safe
Once you have completed the valve and pressure checks, press and hold the reset button (usually marked with a flame and cross symbol) for approximately three seconds until the display acknowledges the reset. Allow the boiler two to three minutes to attempt ignition. If FA returns immediately or after a short time, do not reset repeatedly — further resets will not resolve an underlying mechanical fault and may mask important information for the engineer.
- Check whether the pump was recently replaced or serviced DIY safe
If a heating engineer visited recently to service the boiler or replace the pump and the FA code appeared shortly afterwards, there is a strong chance the pump was refitted in the wrong orientation. Contact the engineer who carried out the work — they should return to correct the installation at no additional cost, as it is their error. Pump reorientation typically takes only 10 to 15 minutes.
- Call a Gas Safe registered engineer to inspect the pump and system Gas Safe engineer
If the reset does not clear the fault, or if the fault returns, a Gas Safe registered engineer must attend to diagnose the root cause. They will check pump orientation, test pump operation, inspect for air locks, and verify all wiring and sensor connections. Depending on findings, they may reorient the pump, bleed the system of air locks, or replace a faulty pump or wiring component. Only once they are satisfied the underlying issue is resolved will they reset and test-fire the boiler.
Parts you may need
- Central heating circulation pump (e.g. Grundfos UPS2 or equivalent) · from £95
- Pump wiring harness / connector · from £18
- Boiler PCB (printed circuit board) · from £180
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £80–£350, depending on the underlying cause.
Frequently asked questions
Can I fix the Ideal FA fault code myself?
Some basic checks are safe for a homeowner — confirming isolation valves are open, topping up system pressure, and attempting a single reset. However, the most common fix (reorienting or replacing the circulation pump) involves working on internal boiler pipework and components, which must be carried out by a Gas Safe registered engineer. Attempting this yourself is unsafe and potentially illegal in the UK.
How much does it cost to fix an Ideal FA fault code in the UK?
For most households, the repair falls between £80 and £350. If the pump was simply installed facing the wrong way after a recent service, the engineer may correct it quickly for a standard callout fee of £50 to £100. A full pump replacement including parts and labour typically costs £150 to £350. In rare cases where the PCB is at fault, costs can rise to £300 to £450 or more, but PCB failure is an uncommon cause of FA specifically.
Why did the FA code appear right after my boiler was serviced?
This strongly suggests the engineer refitted the circulation pump in the wrong orientation. Every pump has a directional arrow that must align with the flow direction in the boiler. If it was reversed during reassembly, the boiler will immediately detect the problem and lock out with FA. Contact the engineer who carried out the service — this is their responsibility to correct free of charge.
Will the FA fault clear itself, or does it need a manual reset?
The FA code will not clear on its own. Once the underlying cause has been identified and corrected by a qualified engineer, the boiler must be manually reset. Simply resetting before the root cause is fixed will either result in immediate re-lockout or temporary operation followed by the fault returning. Always address the cause first.