Boiler fault codes
Ideal Boiler Fault Codes Explained
Ideal boilers show a letter and a number when something is wrong. On Logic and similar models, F codes are faults, some of which clear once the cause is fixed, and L codes are lockouts that wait for the restart button. Find your code below, do the safe checks on its page, and restart only once.
F codes and L codes on an Ideal display
In Ideal's Logic Combi installation manual, the lockout codes include L1 for a flow overheat and L2 for an ignition lockout. The F codes cover faults such as low water pressure (F1), flame loss (F2), the fan (F3) and the flow and return temperature sensors (F4 and F5). Some control boards show the same fault with either letter, so F4 and L4 are both the flow thermistor.
One code catches people out: LC. The board counts restarts, and after five in a quarter of an hour it shows LC and wants the power switched off and on at the fused spur. Pressing restart again and again does not clear a real fault.
Which Ideal codes can you deal with yourself?
Only a few. F1 is low water pressure and is usually yours to fix with the filling loop; Ideal gives 1 to 1.5 bar as the target. F2 and L2 are often caused by something outside the boiler, such as a prepayment meter out of credit, a closed gas valve or a frozen condensate pipe. Everything that means a part inside the casing, such as the fan, a thermistor or the board, needs a Gas Safe registered engineer.
If your boiler is still under Ideal's warranty, contact Ideal first quoting the code, as their own guidance asks. Otherwise, book Ideal boiler repair. You pay the £60 call-out and the repair price is agreed with you on site before any work starts. Gas work is carried out by Gas Safe registered engineers.
If you smell gas, whatever the display says, open windows, turn the gas off at the meter if you can reach it safely, avoid switches, then leave and call the National Gas Emergency Service on 0800 111 999.
Common Ideal codes at a glance
The codes people search for most, each with its own page covering safe checks and what the engineer does:
| Code | What it means | Can you clear it yourself? |
|---|---|---|
| F1 | Low water pressure in the heating system | Yes, once; call if it returns |
| F2 | Flame loss: the flame sensor stopped seeing a flame | Yes, once; call if it returns |
| F3 | Fan fault | No, call an engineer |
| F4 | Flow thermistor (temperature sensor) fault; L4 on some boards | No, call an engineer |
| F5 | Return thermistor (temperature sensor) fault | No, call an engineer |
| F6 | Outside temperature sensor fault | No, call an engineer |
| F9 | Control board not configured or gas valve short circuit (Logic Combi2) | No, call an engineer |
| L1 | Flow overheat or no water flow | Yes, once; call if it returns |
| L2 | Ignition lockout: the boiler failed to light | Yes, once; call if it returns |
| L6 | False flame lockout | No, call an engineer |
| LC | Five restarts in 15 minutes; switch the power off and on | Yes, once; call if it returns |
| L0d | Blocked flue or condensate pipe (Logic Combi2) | Yes, once; call if it returns |
Ideal codes explained
- F1The boiler has measured the water pressure in the heating system as too low to run safely, so it has stopped. Ideal says the pressure needs topping up to between 1 and 1.5 bar.
- F2F2 is flame loss. The boiler lit, or tried to, but the flame sensor stopped seeing a flame, so the gas valve closed and the boiler stopped.
- F3F3 is a fan fault. The control board has not seen the combustion fan run as it should, so the boiler will not light, because it cannot prove the flue gases will be cleared.
- F4On an Ideal boiler, F4 (L4 on some control boards) is a flow thermistor fault: the board is getting a reading from the flow temperature sensor that makes no sense, so it stops the boiler.
Questions people ask
How do I reset an Ideal boiler?
Press and release the restart button on the control panel once. If the display shows LC, switch the boiler off at the fused spur, wait a few seconds and switch it back on. If the same code returns, the cause needs fixing rather than another reset.
Do Ideal fault codes mean the same on every model?
The common ones, such as F1 for low pressure and F2 for flame loss, are shared across the Logic family. Older and commercial ranges can differ, so check the user guide for your model if the code is not listed here.