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Ideal boilers show a flashing letter and number when they lock out. F1 (low pressure) is the one you can fix yourself by topping up the pressure. For L2 or F2 (no flame) there are a few safe checks first. Most other codes need a reset and, if they come back, a Gas Safe engineer.
This page is our Ideal hub. Find your code below and follow the link for the detailed guide where we have one. The codes and advice come from Ideal’s own fault code page. Some models, such as the Logic Max and Vogue, have extra codes, so check your manual if yours is not listed.
| Code | What Ideal says it means | What you can do |
|---|---|---|
| F1 | Low pressure. | Safe to try: top up the pressure to 1 to 1.5 bar, then turn the filling loop fully off. |
| L2 / F2 | Flame loss or ignition lockout. | Safe to try: reset, check prepayment credit and other gas appliances, check the yellow gas isolation valve is open, and thaw a frozen condensate pipe. See our L2 guide. |
| L1 | Flow temperature overheat or no water flow. | Safe to try: open all radiator valves, check the pressure is 1 to 1.5 bar and reset. |
| L3 | No water flow. | Safe to try: check the pressure, bleed the radiators and reset. |
| L5 | Reset too many times in 15 minutes. | Turn the power to the boiler off and on again. |
| L6 | False flame lockout. | Reset. If it returns, Gas Safe engineer only. |
| F3 | Fan fault. | Reset. If it returns, Gas Safe engineer only. Do not try to check, clean or replace the fan. |
| F4 / F5 / F0 | Flow, return or water flow thermistor (sensor) fault. | Reset. If it returns, Gas Safe engineer only. |
| F6 | Outside sensor fault. | Reset. If it returns, engineer. |
| F7 | Low mains voltage. | Have an electrician check the electrics. |
| C0 / C2 | Boiler control chip (BCC) fault. | Reset. If it returns, Gas Safe engineer only. |
One reset is fine. If the same code keeps coming back, stop resetting and book an engineer.
The gauge has dropped below 1 bar. Top it up with the filling loop (see how to repressurise a boiler) and reset.
Always make sure the filling lever or external filling loop valves underneath are turned completely off once the gauge reaches between 1 and 1.5 bar. If left cracked open, mains water will continue to push in, sending the pressure over 3 bar, putting stress on the boiler components and discharging water outside through the pressure relief pipe.
If you have to top up again within a few weeks, there is a leak, often a weeping radiator or towel rail valve.
The boiler could not light or lost its flame. Check prepayment credit, other gas appliances and the yellow gas isolation valve under the boiler, and in cold weather pour warm (not boiling) water along the outside section of the plastic condensate pipe, then reset the boiler. Our L2 guide covers this step by step.
Gas Safe engineer only The fan is inside the sealed boiler casing. Reset once, and if F3 returns, book an engineer. Do not try to check, clean or replace the fan yourself.
Gas Safe engineer only Codes that point to the control board or its chip (C0, C2) need an engineer to test and, if needed, replace the board. On an older boiler, a new board can cost enough that a replacement boiler is worth pricing too.
Safe for you to try
Gas Safe engineer only
Always check your engineer is on the Gas Safe Register.
If you smell gas, do not reset the boiler. Turn off the gas at the meter if you can, open the windows, do not use switches or naked flames, leave the property and call the National Gas Emergency Service on 0800 111 999.
From the job: Ideal Logic+ topped up every week
Ideal Logic+ owner topping it up every week to clear F1. Traced it to the valve on the bathroom towel rail, which was weeping under the floor. Replaced the valve, refilled, and it’s held pressure since.
Expert notes by Kevin Saban, Gas Safe registered engineer (Gas Safe ID 6115119), Homecure Plumbers – Gas Safe Reg 505421
Our engineers repair Ideal boilers across London. Repairs from £95 + VAT for the first hour, including diagnosis (or a fix if it can be done within the first hour with no parts needed), no callout charge. Prices apply during office hours; parking or the congestion charge may be added. See our boiler repairs page or call 0203 504 4000.
Both are fault codes. L codes are lockouts, where the boiler has shut down for safety until it is reset. F codes are faults, such as low pressure (F1) or a failed sensor.
Once a year by a Gas Safe registered engineer.
Sources: Ideal: boiler fault codes · Gas Safe Register