Ideal Boiler Fault Codes

Even boilers have faults from time to time. As a result, like any other boiler, Ideal boilers could develop a wide range of faults.

In this post, we'll cover

Even boilers have faults from time to time. As a result, like any other boiler, Ideal boilers could develop a wide range of faults. Specific Ideal boiler problems can cause the boiler to go into a safety lockout mode, where fault code information will be displayed. You can find the appropriate Ideal boiler fault codes together with Ideal boiler troubleshooting solutions.

A fault in the boiler may cause it to lock out to prevent further damage and display an error code to help you or your gas-safe engineer identify the issue and help fix it before resetting the boiler.

Take a look at what each fault code means to find your model, your fault code, and then the real issue and how it can be fixed. 

Different ideal boiler fault codes:

‘F’ Fault code:

Fault Codes

The Issue

How You Can Fix It

FD- No water flow

A fault during the installation might cause airlocks in your system, pump, or wiring. If there is a shortage of water in the central heating system or issues in water circulation might also result in FD. 

Here, the issue is not with the boiler but with its installation. By repressurising your boiler, you may be able to resolve this issue. If this does not work, we recommend contacting your installer to inspect your heating system and correct it.

F1- Low water pressure

Insufficient water flow in your heating system will cause low water pressure, leading to an F1 error.

Mostly, you can fix this issue yourself by topping up your boiler's water pressure to 1.5 using the in-built filling loop. However, if the issue is still prolonged, you may contact a Gas Safe registered engineer.

F2- Flame loss

An F2 error denotes the loss of flame during operation. However, it could be caused by more profound system errors, such as faulty gas pressure, an issue with your flue, a defective gas pressure, any issues in the flue, a faulty gas valve, a wrongly adjusted valve, or a fan malfunction.

To fix the Ideal boiler f2 fault code, you must first check all the other gas appliances and then try resetting your boiler. However, this fault commonly occurs in older and low-efficiency boilers, so it might be best to install a new boiler.

F3- Fault with the fan

A loose or damaged fan is to blame for this problem. However, the problem may stem from deeper issues such as loose connections, water damage from a boiler leak, a faulty air pressure switch or a faulty printed circuit board.

In cases where you come across an F3 fault code, you will need the assistance of a qualified engineer to resolve it because the problem can have various causes,  and the costs can vary.

F4- Thermistor fault

An F4 fault code indicates a problem with the flow thermistor or the boiler's operation, but, again, circulation issues are most likely the culprit.

An engineer registered with Gas Safe will have to resolve this fault.

F5- Return thermistor fault.

The return thermistor may be malfunctioning, or its operation may be faulty. Possible causes are a defective NTC returns thermistor, a damaged connection, a significant temperature differential between the flow/return thermistor, or a wrongly printed circuit board.

You will need to reach out to a Gas Safe registered engineer who will be able to resolve this fault.

F6- Outside sensor fault

An F6 fault code usually results from a broken or faulty outside sensor on your system, which usually results in an F6 fault code. You may also have a problem with the printed circuit board of your boiler, which is generally more expensive to fix.

A weather compensator might be the cause of this problem. You need to contact a qualified engineer if you don't have a weather compensator, or if it wasn't recently installed.

F7- Low mains voltage

Suppose it could be that your property's main electricity source is causing this fault code. Your boiler will automatically cease operations as a safety precaution when it detects this fault.

If a voltage drops below 190 volts at the boiler, this might not be a boiler fault. Contact your installer.

F9- Printed circuit board fault

An unconfigured printed circuit board (PCB) results in the F9 fault code.

You should get a new boiler installed instead of repairing it as it is a costly process.

L Fault Codes:

Fault Codes

The Issue

How You Can Fix It

L1- Lack of water flow

When the boiler's resistance readings are too low or too high, the boiler stops working and displays a fault code as a safety precaution.

You need to reset your boiler if L1 appears. A qualified engineer should be contacted if this does not help. Overheating issues occur in older boilers frequently and are common. So, investing in a new boiler would be worth it.

L2- Ignition lockout

This will be an uninformed boiler lockout for safety reasons, and the exact cause needs to be identified.

Any rumbling coming from the system denotes that your condensate pipe or the flue has some issue. Reset the boiler and then call an engineer to diagnose the issue.

L3- No flow thermistor fault

A wrong boiler chip card is the culprit here. An L3 fault code denotes that the printed circuit board (PCB) has been changed, and there is a wrong boiler chip card (BCC) inserted.

First, check your system’s pressure reading. You may also bleed your radiators to see if that helps. If nothing seems to work out, call a gas-safe engineer as it might be due to any complex issue.

L5- Problem with the boiler in return type

Resetting the boiler five times in 15 minutes can cause an L5 error.

The boiler's power should be shut off at the fuse spur and then turned back on. If the problem continues, contact a qualified engineer.

L6- Flame detection fault

An L6 fault code occurs when there is a false flame detected in the boiler while there is no demand for heat or hot water. This will lead to a boiler lockout.

Your boiler should be reset. However, should the boiler still not operate and your warranty covers your system, you should contact the manufacturer.

LF- Ignition fault

The boiler may have been 'locked out' as a safety precaution. 

We recommend resetting your boiler after ensuring that all other gas appliances in your home are working. An obstruction in the condensate pipe could cause your boiler to rumble. Consult a qualified engineer.

L9/H9/HA/LA- Overheating

When the temperature of your resistance reading is too high, the L9/H9/HA/LA fault code appears.

Ensure your system's pressure is correct. You can also bleed your radiators to see if this helps. We recommend you to contact a Gas Safe registered engineer since the overheating could be caused by a fault in the boiler's pump or dry fire stat.

C Fault codes:

Fault Codes

The Issue

How You Can Fix It

C0- Central heating signal issue.

Due to poor circulation, your boiler may go into pump overrun if you still have hot water. This will be indicated by an alternating on and off of your thermostat signal.

Call a qualified engineer to check your room thermostat and radiator circulation, to rectify this issue.

C2- Fault with the boiler chip card

An activation fault or internal error has occurred on the boiler chip card in the ideal boiler status C2.

If your boiler is not working, try resetting it. If it still doesn’t work, call a gas-safe registered engineer.

Other Faults:

Fault Codes

The Issue

How You Can Fix It

No display

Any issue with your printed circuit board will result in a boiler fault.

The power button at the fuse spur needs to be turned off first and then on. Contact our repair team if this doesn't work. It would be better to contact your installer first if you have recently had electrical work done on the system.

Noisy operation

Central heating systems are prone to kettling issues. In addition, it may indicate loose components or high pressure if you hear a humming or rattling noise.

We suggest you check for loose components or repressurise your boiler to fix this problem.

High gas bills

The way you use heating will also affect your gas bill, and the efficiency rating of your boiler will keep increasing if the usage is high or inappropriate.

Make sure your boiler is labelled as efficient. We suggest you invest in only A-rated heating systems.

Noisy ignition

This happens only if there’s an issue with your condensate pipe, flue, or gas.

You can resolve this only by calling a gas-safe registered engineer.

Additional Troubleshooting Tips:

When to call a gas-safe engineer:

For most "F" and "L" fault codes: These faults often involve internal components like the PCB, thermistors, or gas. Attempting DIY repairs can be dangerous and void your warranty.

If the fault code persists after recommended troubleshooting: Resetting the boiler may resolve simple issues, but recurring faults indicate deeper problems requiring professional attention.

For any gas-related issues: Gas leaks, faulty gas valves, and ignition problems pose safety risks and should only be handled by a qualified gas-safe engineer.

When signs of water damage are present: Water damage near the boiler can affect electrical components and lead to further complications.

If unusual noises occur: Loud banging, kettling sounds, or persistent humming can indicate loose components, pump problems, or internal blockages, requiring professional diagnosis and repair.

For any suspected leaks: Leaks from the boiler body, valves, or pipes can signify internal corrosion or loose connections, requiring immediate attention from a qualified engineer to prevent further damage and potential water damage to your home.

Before replacing the boiler: While some fault codes might suggest a new boiler, a Gas Safe engineer can assess the situation and recommend repairs if feasible, potentially saving you money.

Boiler maintenance tips to prevent faults:

Regular servicing (annually): A Gas-safe engineer can perform a thorough inspection, clean the boiler, and identify potential issues before they escalate into faults.

Checking water pressure: Maintain the water pressure between 1 and 1.5 bar using the filling loop. Low pressure can trigger faults, while high pressure can damage components.

Bleeding radiators: Trapped air in radiators can cause uneven heating and reduce boiler efficiency. Bleed the radiators regularly to release air and ensure optimal performance.

Checking the flue and condensate pipe: Blockages in the flue or condensate pipe can prevent proper ventilation and lead to overheating or boiler lockout. Ensure they are clear and free of debris.

Using a Magna clean filter: This filter traps impurities in the central heating system, preventing them from reaching the boiler and causing blockages and potential faults.

Insulating pipes: Insulating hot water pipes reduces heat loss and improves boiler efficiency, saving you money on energy bills.


Boilers provide both warmth and hot water for your home, so they need to run efficiently. Get boiler breakdown insurance and cover mechanical failures, faulty controls, and other boiler problems. 

Reach out to us today. 

Maintain your home's heating system with ease by exploring our blog on " How to Reduce Boiler Pressure." Navigate through practical steps, expert insights, and troubleshooting tips to ensure optimal boiler performance.