Ideal boiler fault codes explained

FD: No water flow

The problem

This fault could stem from issues with your system’s air locks, pump or wiring due to the fault during installation. This could also be caused by a lack of water in your central heating system or an issue with water circulation.

The solution

This isn’t an issue with your boiler but with its installation. You could try to solve this fault by repressurising your boiler, however, if this doesn’t help, we recommend you call your installer to inspect your heating system and rectify the issue.

F1: Low water pressure

The problem

If your heating system doesn’t have enough water, this fault can occur as its pressure could become low.

The solution

It is usually possible for you to fix this issue yourself by topping up your boiler’s water pressure to 1.5 using the in-built in filling loop. If you’re still facing issues, contact a Gas Safe registered engineer.

F2: Flame loss

The problem

This usually means that there has been a flame loss during operation. This issue could be caused by deeper system errors such as incorrect gas pressure, an issue with your flue, a faulty gas valve, an incorrect adjustment of a valve or a fan fault.

The solution

Firstly, check other gas appliances and you could try to reset your boiler. This fault typically occurs with older boilers and low-efficiency systems, so it may be worth considering getting a new boiler installed.

F3: Fault with fan

The problem

This fault is caused by a loose or damaged fan. This issue could be related to deeper problems such as loose or damaged connections, water damage from a boiler leak, a fault with the air pressure switch or a problem with the printed circuit board.

The solution

This fault will require the help of a qualified engineer. As the issue can stem from a range of different causes, costs can vary.

F4: Thermistor fault

The problem

The F4 fault code tends to signify a problem with your boiler’s flow thermistor or an issue with its operation. The fault will typically be related to circulation issues.

The solution

This fault will require a call-out to a Gas Safe registered engineer.

F5: Return thermistor fault

The problem

This refers to a fault in the return thermistor or its operation. Usually related to a faulty NTC return thermistor, a damaged connection, a differential in temperature that’s too high between the flow/return thermistors, or a faulty printed circuit board.

The solution

This fault will require a call-out to a Gas Safe registered engineer.

F6: Outside sensor fault

The problem

This fault code will usually show if your system’s outside sensor is broken or faulty. This can also be related to your boiler’s printed circuit board, which is typically more expensive to fix.

The solution

Recently had a weather compensator fitted? This fault could be related to its installation. If your weather compensator wasn’t installed recently, or if you don’t have one at all, call a qualified engineer.

F7: Low mains voltage

The problem

If you notice this fault code, there could be an issue with your property’s mains electricity source. As a safety precaution, your boiler is built to cease operations once it identifies this fault.

The solution

The voltage to the boiler has dropped below 190 vol. This is not a boiler fault, but we recommend you contact your installer.

F9: Printed circuit board (PCB) fault

The problem

The F9 fault code on your Ideal boiler typically relates to an unconfigured printed circuit board (PCB).

The solution

Repairing this fault could be a costly expense. It may be worth considering getting a brand-new boiler installed.

L1: Lack of water flow or problem with temperature readings

The problem

The L1 fault typically indicates that the boiler has detected low water flow or that the hot water flow temperature is outside the normal range, either too high or too low.

Your boiler takes resistance readings, which are then sent to the printed circuit board, and if the temperature reading is too low or too high, the boiler will cease to work as a safety precaution and display a fault code.

The solution

Reset your boiler. If this doesn’t help, you should then contact a qualified engineer. Overheating is generally an issue that happens with older, less efficient boilers, so it may be worth investing in a new heating system.

You should also check the boiler’s pressure gauge. If it’s below the recommended level (usually between 1 and 1.5 bar), you might need to repressurise the system using the filling loop or contact a Gas Safe engineer for help.

L2: Ignition lockout

The problem

Your boiler has been ‘locked out’ as a safety precaution. The cause behind this will need to be identified.

The solution

Reset your boiler. If there’s rumbling coming from the system, this suggests your condensate pipe is blocked or that there is an issue with your flue. This requires a call-out from a qualified engineer.

L3: No flow thermistor fault

The problem

This fault code typically indicates that someone has changed the printed circuit board (PCB) and used the wrong boiler chip card (BCC).

The solution

This requires a call-out from a qualified engineer.

L9/H9/HA/LA: Overheating

The problem

Like L1, this code could indicate that the temperature on your resistance reading is too high.

The solution

Check your system’s pressure reading, you could also bleed your radiators to see if this helps. If not, we recommend contacting a Gas Safe registered engineer as the overheating could be a result of a deeper issue with your boiler’s pump or dry fire stat.

LF: Ignition fault

The problem

Your boiler may have been ‘locked out’ as a safety precaution. The cause of this will need to be addressed.

The solution

Check that other gas appliances in your home are working, if so, we recommend that you then reset your boiler. If your boiler is rumbling, there could be a blockage in your condensate pipe. Contact a qualified engineer to fix the issue.

L5: Problem with the boiler return pipe

The problem

This could occur if someone resets the boiler 5 times in 15 minutes.

The solution

Turn off the boiler’s power at the fuse spur, then turn it back on again. If the issue continues, contact a qualified engineer.

L6: Flame detection fault

The problem

This usually happens when your flame comes on before your gas.

The solution

Reset your boiler. If the boiler still fails to operate and your system is still covered by your warranty, you could contact your manufacturer for assistance.

C2: Fault with the boiler chip card

The problem

The boiler chip card has an internal error or an activation fault.

The solution

Try resetting your boiler. If this doesn’t help, contact a Gas Safe registered engineer.

C0: Central heating signal issue

The problem

If your domestic hot water is still working, your boiler could be going into pump overrun due to poor heating circulation. Alternatively, your thermostat signal could be cutting in and out.

The solution

To help rectify this issue, we recommend you seek the help of a qualified engineer to check your room thermostat and your radiator circulation.

Other Ideal boiler faults

No display

The problem

There is an issue with your printed circuit board.

The solution

Turn the power off at the fuse spur and turn it back on again. If this fails, contact our repairs team for assistance. If you’ve recently had electrical work completed on the system, it may be best to contact your installer first.

Noisy operation

The problem

Issues such as kettling tend to be common issues with central heating systems. A humming or rattling noise could indicate issues such as loose components or high pressure.

The solution

To help solve this issue, you could check the system for loose components or try repressurising your boiler. If these measures do not help, contact our repairs team.

Noisy ignition

The problem

This could indicate a problem with your system’s condensate pipe, gas or flue.

The solution

We recommend seeking the help of a Gas Safe registered engineer.

No/poor hot water

The problem

If your heating is working but your hot water is not being delivered as usual, it typically won’t be a fault with the boiler.

The solution

We recommend seeking the help of a Gas Safe registered engineer.

No/poor central heating

The problem

If your hot water is working, then this is not typically a fault with the boiler, but instead a problem with your radiators.

The solution

If poor or no central heating is an issue, then contact our repairs team. This fault could be expensive to fix, but getting a new boiler installed could prove to be effective.

High gas bill

The problem

This could be due to the efficiency rating of your boiler, your energy bill could also be impacted by the way in which you are using your heating.

The solution

Check your boiler’s efficiency label. It could be beneficial for you to invest in a new A-rated heating system.

Pressure loss

The problem

This usually means that water is escaping somewhere in the system, or alternatively the issue could be due to the expansion valve failing and thus causing damage to the pressure release valve.

The solution

Firstly, follow our guide on how to repressurise your boiler. If this becomes a continuous issue, then check for leaks, if none are found, get in touch with our repairs team.

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