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Common Ideal Boiler Problems


Ideal Boilers was created in 1906.  It has more than a century of experience offering customers high-quality heating solutions. They are currently one of the boiler market leaders and help in pioneering new boiler technology.

But regardless of their quality, Ideal Boilers breakdown from time to time. And no, it’s not fun having to make do without hot water or heating especially when you have a family to attend to. Luckily, Ideal boilers come with fault codes that make boiler troubleshooting a breeze.

Here are some common Ideal boiler problems along with their fault codes and fixes.

No water flow

This could be caused by a myriad of problems ranging from an airlock in the boiler system, faulty pump or incorrect wiring during Ideal boiler installation. Moreover, it could also mean there’s no water in the system or the circulation system has a fault.

Ideal boilers will give an FD fault code to make your diagnosis easier.


Usually, this isn’t a problem with the boiler system but with the installation. You could try and fix the problem by repressurizing the boiler. But if that doesn’t work, call a Gas Safe engineer to inspect the system and fix the problem.

Low water pressure

Ideal boilers naturally lose pressure over time. However, the sudden loss of pressure signifies a problem in the boiler system. The most common causes of low water pressure include;

  • Water leaks
  • Bleeding radiator

Water leaks can occur on the boiler pipes, radiators or boiler. They can often be difficult to spot but with a keen inspection, you’ll notice water pools and dampness in some sections.  On the other hand, when you bleed boiler radiators, you release air and consequently lower boiler pressure.

And though low boiler pressure should not cause panic, if not attended to, can cause boiler inefficiency and a spike in energy bills. Ideal boilers have pressure gauges to track boiler pressure. When boiler pressure is low, the gauge reads below 1 bar. Also, Ideal boilers an F1 fault code.


You can repressurize the boiler by adding water through the filling loop. During the process, keep an eye on the gauge ensuring it doesn’t go past 1.5 bar.

If after repressurizing you still experience problems, it’s probably an internal leak and you should contact a Gas Safe engineer for a fix.

Flame loss

A stable flame is essential for efficient boiler performance. Boiler flame loss is not only an inconvenience but also exposes you to the risk of an explosion. Flame loss during boiler operation is caused by system errors including:

  • Faulty flue
  • Faulty gas valve
  • Incorrect gas pressure
  • Fan fault
  • Incorrect valve adjustment

In Ideal boilers, a flame loss fault is denoted by an F2 fault code.


First, check your gas connection and if other gas appliances are working. If the connection is fine, try resetting the boiler.

Usually, flame loss occurs in old boilers. As such, you should consider installing a new boiler.

Overheating boiler

Overheating puts your Ideal boiler at the risk of explosion. Luckily, Ideal boilers have safety features which lockout the boiler before the temperatures get too high. The lockout also helps to prevent further boiler damage. Usually, Ideal boilers display L9/H9/HA/LA fault codes to help you diagnose the problem.

Causes of boiler overheating include:

  • Limescale build-up
  • A block in the system
  • Faulty pump
  • Thermistor problem


Once you notice signs of overheating, turn off the boiler water supply. Not turning off the water supply means cold water will enter the system, turn into steam and increase boiler pressure to dangerous levels.

Once the water supply is off, call in a Gas Safe engineer to diagnose and fix the cause. If its limescale build up or a bloc in the system, he will flush the system. And if it’s a faulty pump or thermistor, he will repair or replace.

Fan Fault

The fan is an important boiler part. It runs and creates a draught to fan harmful gases into the boiler flue for expulsion. Air pressure in the boiler is tracked by an air pressure switch. Without a working fan, the air pressure switch will pick up on incorrect boiler air pressure and send feedback to the PCB. The PCB then locks out the boiler to prevent poisoning.

You ideal boiler will display an F3 fault code.


Call a Gas Safe boiler engineer to repair or replace the fan. For a replacement, expect to part with about £250. Fan replacement is grounds for a new boiler installation. But if the PCG or gas valve need replacing as well, then you should consider a new boiler installation.

Mains voltage

When your Ideal boiler displays an F7 error code, it’s unlikely that it is dangerous.  The boiler should be locked out. The cause of this error is a mains voltage fault. The fuse may be blown or the circuit may be faulty


Given that it’s a power issue, you can call an emergency electrician or a Gas Safe engineer. They will inspect the boiler and isolate the cause of the fault.

At times, even after the main voltage fault is fixed, the boiler may fail to start up because of damaged electrical boiler components. The Gas Safe engineer will inspect the electronic parts for potential damage. They will focus on the PCB.

Unresponsive boiler

The PCB controls most electronic components. It receives and sends signals allowing the boiler components to operate in synchrony. Therefore, if the PCB doesn’t work the boiler doesn’t either.

The F9 fault code points to an incorrectly configured PCB. This often happens in new boilers or after an installation of a new PCB. But at times the fault code is also linked to faults in boiler chip card activation in which case you’ll receive C0 or C2 fault codes.


The Gas Safe engineer will inspect the PCB configuration and the operation of the chip card.

No hot water

There are two scenarios you can encounter:

  • You have heating and no hot water
  • You have no heating and no hot water

These scenarios are caused by several factors including:

  • Pilot light is off
  • Frozen condensate pipes
  • Faulty diverter valve
  • Pressure mishaps including over and under pressurization

Depending on the cause, the boiler will display different fault codes including L2, F2, LN or FN.


If it’s a pressure issue, a quick DIY repressurizing or depressurizing will work. For other faults, call a Gas Safe engineer for diagnosis and a solution.

Big bang during turn on

This problem has probably scared you more times than you care to remember. The problem occurs when there is a lot of gas before boiler ignition. When the boiler is fired up, on the 3rd attempt, a mini-explosion occurs. The fault code displayed


The common cause of the big bang is the failure of flame detection. Have a Gas Safe engineer inspect the flame sensors and the ignition leads.

Next, they will inspect the amount of gas flowing into the chamber and adjust the fan speed.

Faulty Thermistor

Boiler thermistors are thermally sensitive resistors. They can:

  • Measure temperature
  • Compensate for changes in temperature
  • Changes in temperature

The resistance is often determined by the absolute temperature. A broken thermistor is characterized by inefficient heat transfer and uncomfortable temperature changes. An Ideal boiler displays an F4 fault.


A Gas Safe engineer should replace the thermistor.

Other fault codes and troubleshooting

Fault code CO: Central heating fault.

How to fix – Call a Gas Safe engineer to inspect the radiator circulation and room thermostat.

Fault code L5: boiler return pipe fault.

How to fix – Turn off power at the fuse spur and turn it back on. If the problem persists call a Gas Safe engineer.

Fault code LF: Ignition fault.

How to fix – if other gas appliances are operational, reset the boiler. If there’s a rumbling, unblock the condensate pipe.

Fault code F6: Outside sensor fault.

How to fix – Call a Gas Safe engineer to reinstall the weather compensator.

Fault code F5: Return thermistor fault

How to fix – Contact a Gas Safe engineer

Should you replace your ideal boiler?

If your boiler is more than 10 years old, you should consider buying a new one. A new boiler will help you save up to £305 depending on the size of your home and the number of occupants.

Who should you use for the repairs and boiler replacement?

Once you decide to buy a new boiler, think about the professional you hire. Whoever you choose should be Gas Safe registered. You can opt for a local engineer or a national UK company.

A national company will offer additional services including an ongoing boiler cover and brand protection on the other hand, local engineers have competitive rates and offer personalized services.

We recommend getting several quotations to get the best deal.

How to improve your boiler’s life?

Ideal boiler warranty

Depending on the Ideal boiler you buy, you’ll get a warranty ranging between 2 and 10 years. But if you fail to register your new boiler 30 days after its installation, you are limited to a 1-year warranty.

And once the initial warranty expires, Ideal offers an ‘Out of Warranty Protection’. The warranty covers you for 12 months and costs £1,500. It covers repair costs including labour, parts and call-out fees.

The Ideal Max boilers come with a standard 10-year warranty. However, if the installation is done by an accredited Max installer, you get 2 years extra.

Now, the warranty covers the full cost of labour and parts when the Ideal boiler suffers an electrical or mechanical breakdown courtesy of poor workmanship or defective materials.

To maintain the warranty, you need to conduct an annual boiler service and to use a Gas Safe registered engineer.

Ideal boiler service

With the right amount of servicing and maintenance, an ideal boiler cold last up to 15 years. The most important is the annual servicing where the Gas Safe engineer performs standard checks including:

  • Inspecting your Ideal boiler and ensuring the pilot light burns blue.
  • Cleaning the heat exchanger.
  • Ensure the flue isn’t blocked.
  • Confirm gas levels and flow settings
  • Fire up the boiler to check its performance

The annual service is important for:

  • Safety
  • Keeping energy bills low
  • Preventing frequent breakdowns
  • Maintaining Ideal boiler warranty

On average, the annual Ideal boiler service will cost about £100. The cost depends on your location, the Gas Safe engineer you hire, and the repairs needed.

Reach out to us today for 4 free quotations from Gas Safe registered engineers. We are dedicated to ensuring you get the best possible service and that your boiler last long.

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