Common Ideal Boiler Fault Codes:
Here are some of the most frequently encountered Ideal boiler error codes:
1. F1 – Low Water Pressure
This is one of the most common Ideal boiler fault codes, indicating low system water pressure (below 1 bar). The boiler will typically lock out as a safety precaution.
Water loss from the heating system (e.g., small leak in radiators, pipes, or boiler components).
Pressure naturally drops over time (very gradual).
Recently bled radiators.
Faulty pressure sensor.
Check the pressure gauge on your Ideal boiler; it should typically be between 1 and 1.5 bar (when cold).
If low, you can often re-pressurise the system using the external or internal filling loop, following your Ideal boiler’s specific manual instructions carefully.
If you repressurise the boiler and the F1 code returns frequently, it suggests a leak in the system or a faulty pressure sensor, requiring professional investigation.
2. F2 / FL – Flame Loss / Ignition Fault
This code indicates that the boiler ignited, but the flame then extinguished during operation, or it failed to ignite at all.
Interruption to the gas supply (e.g., gas meter valve closed, low gas pressure).
Frozen or blocked condensate pipe (especially in cold weather).
Faulty ignition electrode or lead.
Faulty gas valve.
Issues with the fan or flue (preventing proper combustion).
Ensure your gas supply is on and other gas appliances (like your hob) are working.
Check for a frozen condensate pipe outside your property (a white/grey plastic pipe, often near a drain). If frozen, you may be able to gently thaw it with warm water (consult your manual), then try resetting the boiler.
You can try resetting the boiler (usually by pressing a reset button, or turning the boiler off and on at the fused spur).
The F2/FL code often points to a safety-critical issue with the gas supply or ignition system. Immediately call a Gas Safe registered engineer.
3. F3 – Fan Fault
This code indicates a problem with the boiler’s fan, which is vital for the combustion process, removing exhaust gases, and drawing in fresh air.
Faulty or seized fan motor.
Blockage in the flue or air intake.
Faulty air pressure switch.
Wiring issues to the fan.
Visually inspect the flue terminal outside your property for any obvious obstructions (e.g., bird’s nest, debris).
You can try resetting the boiler.
An F3 fault is a safety-critical issue related to flue gases. Do not attempt to fix this yourself. A Gas Safe registered engineer must diagnose and repair the fan or related components
4. L2 – Ignition Lockout / No Flame Detected
Similar to F2, this code means the boiler has failed to ignite after multiple attempts and has gone into lockout mode as a safety precaution.
No gas supply.
Frozen condensate pipe.
Faulty ignition electrode or gas valve.
Issues with the boiler’s PCB.
Air in the gas pipework (especially after gas work).
- Ensure your gas supply is on.
- Check for a frozen condensate pipe and attempt to thaw it.
- Try resetting the boiler.
If resetting doesn’t work, this is a safety-critical fault that requires a Gas Safe registered engineer to diagnose and repair the underlying ignition or gas supply issue.
5. L5 – Boiler Has Experienced Too Many Resets (Overheat Lockout)
This is a safety lockout code. It indicates the boiler has attempted to reset itself too many times within a short period (often 15 minutes) due to a persistent underlying fault, commonly overheating.
Previous, unresolved fault (e.g., circulation issue, pump fault, blocked heat exchanger) causing repeated overheating.
Faulty safety temperature limiter or sensor.
Air in the system or closed valves.
Ensure all radiator valves are fully open.
Check that the system pressure is adequate (1-1.5 bar).
You can try turning the boiler off at the fused spur for a few minutes, then turning it back on to attempt a deeper reset.
An L5 fault is a serious indicator of an underlying issue that the boiler cannot resolve. It requires immediate professional attention. A Gas Safe engineer will need to identify the root cause of the persistent fault.
6. F4 / L4 – Flow Thermistor Fault / Overheat
This indicates an issue with the flow thermistor (temperature sensor) or that the flow temperature is too high. The boiler is not correctly sensing the temperature of the water leaving it.
Faulty flow thermistor.
Wiring issues to the sensor.
Poor water circulation (e.g., pump fault, blockages, air in the system).
Main PCB fault.
Ensure all radiator valves are open.
Check system pressure.
This often requires professional diagnosis to determine if it’s a sensor fault, a circulation problem, or a more serious internal issue.
6. F4 / L4 – Flow Thermistor Fault / Overheat
This indicates an issue with the flow thermistor (temperature sensor) or that the flow temperature is too high. The boiler is not correctly sensing the temperature of the water leaving it.
Faulty flow thermistor.
Wiring issues to the sensor.
Poor water circulation (e.g., pump fault, blockages, air in the system).
Main PCB fault.
Ensure all radiator valves are open.
Check system pressure.
This often requires professional diagnosis to determine if it’s a sensor fault, a circulation problem, or a more serious internal issue.