Boiler PCB Faulty? What Is a PCB and How You Fix It

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Last updated: October 31, 2023

Often described as the brains or nerve centre of your boiler, the Printed Circuit Board – or PCB – is a vital component of your central heating and hot water system. So, if you experience problems with the PCB, both you and your boiler will know about it. Without a fully functioning PCB your boiler will struggle to run effectively and supply you with the heat and hot water you need. And should it break down, then getting the PCB back on track isn’t a cheap fix.

We take a look at exactly what as boiler PCB does and what you should do to fix it, should things start to go wrong.

What Is A Boiler PCB?

A crucial component of modern boilers, the Printed Circuit Board is effectively the control centre of your system as it is where all the electronic components in your boiler get their instructions from. This PCB control centre also enables the components to ‘communicate’ so they work in synchronicity to keep the boiler functioning as it should. You could also think of the boiler PCB as the conductor of an orchestra, for example, so that the pilot light will ignite, the PCB will bring the rest of the team on board, starting with the fan to create the right air pressure and then open up the gas valve ready for the boiler to ignite and start up.

The PCB also has feedback loops and constantly monitors the boiler. This means that if there’s an issue or fault with any of the electronic components, an error code will be triggered on the boiler display panel, and even a lockout so that the boiler is protected from any further or potential damage.

Symptoms Of A Faulty PCB

With such an essential component, should the PCB develop a problem, it will have a knock-on effect to the rest of your boiler, potentially impacting on your heating and hot water supply if not resolved. So, knowing what the symptoms of a fault PCB are to look for will give you a head-start on getting everything back on track. However, it is important to point out that if you do suspect a faulty PCB you should call out a Gas Safe registered engineer to further investigate. Printed Circuit Boards are part of the internal workings of your boiler, and you could damage your boiler and even invalidate your warranty if you attempt a repair yourself.

As a guide, here are the main signs that you may have an issue with your Printed Circuit Board:

Burning Smell 

A burning smell from your boiler is a cause for further investigation. And, when it comes to the PCB, any smell of burning could indicate parts of the circuit board have burnt out. Typically, you should also see an error code, or the boiler will lockout – which means the system has shutdown to protect the boiler from further damage and to prevent it from becoming a more dangerous situation. A burnt-out Printed Circuit Board PCB will need replacing completely so never ignore that burning smell.

Display Panel not Working Properly

If you notice your boiler’s display panel is working intermittently or struggling to light up, this could indicate a loose connection with the PCB. But before you call out a heating engineer you do need to double check your boiler manual as some models have a flashing interface as a way of indicating another error or that it is time for your boiler to be serviced. However flickering lights or an intermittently working display could be a sign that there is something going on with the PCB.

No Power

If your PCB has experienced a total power out, then it is likely you will have no display or working boiler. There is no denying a power cut out, so this is one of the potential PCB faults that needs urgent professional attention from a Gas Safe engineer.

Sporadic Operation

With the PCB being the heart of all your boiler components, if it starts to malfunction it will miscommunicate and can cause some or all of these components to also struggle. And chances are, you will see the impact in a sporadic boiler performance.

Memory Fault

If you see an error code on your boiler display that indicates a ‘memory fault’ then this is a sign your PCB needs to be reset or reconfigured. This is usually seen if you have a new boiler that has just been installed or if you have had your Printed Circuit Board replaced.

Wiring Issues

Wiring inside your boiler is the lifeline that connects the PCB to all its electronic components. So, if there is an issue, for example with a loose wire, then there will be a disruption to how well these boiler components, and by association your boiler, functions. And if the wiring issue cause a faulty PCB, you may also find your boiler locks out (shuts down) to prevent any further damage until the problem is fixed. Examples of disruptions caused by loose wiring include a broken connection between the PCB and the boiler’s gas valve or heat exchanger. And these disruptions will cause obvious issues with how well your central heating and hot water supply work.

Fault Finding With Boiler PCBs

Ok, so you may be able to identify an issue with your PCB but taking the next step to finding the actual fault with your Printed Circuit Board is not a quick fix. And this is because there are a host of reasons why your PCB is not working as it should.

As the PCB is an electronic component, and links to other essential components within your boiler, you need to get a professional heating engineer out to investigate exactly what is going on and identify the PCB fault.

When there is an issue with a boiler’s PCB, there’s a list of fault finding your engineer will be able to work through to work out if it can be fixed or if the best solution is to replace your old boiler with a new one:

A Leak

A water leak in your boiler can be disastrous for the PCB and even a small leak can cause havoc. A water leak inside the boiler creates a build-up of moisture which seeps into electrical components such as the ignition as well as the PCB itself, potentially causing it to burn out.

The most likely culprits for a boiler water leak are the pump or the heat exchanger. The heat exchanger, which heats the water inside the boiler before it is circulated into your heating and hot water system, is prone to cracking, especially if it is old or limescale has been allowed to build up. As the water runs through the exchanger it will seep and then eventually leak out and onto the PCB and other electronics.

Meanwhile the boiler pump, can suffer from degraded or blown seals over time, especially if it is put under strain due to sludge blockages. These torn seals are another cause of a water leak inside your boiler and can cause expensive or even irreparable damage to the PCB and electronics.

Boiler Vibrations

small vibrations and low-level noise is normal for a boiler system. But if you have noticed that your boiler is getting consistently noisy or is vibrating more than normal then you need to get it checked out. Excessive vibrations from the pump or the fan, for example, can damage the boiler’s internal components, including the PCB if left unchecked. PCBs are fragile and prone to breaking if put under pressure so when you get your boiler checked for noise and vibration, ensure the engineer checks the electrics too.

Cracks and Fractures

if your boiler, and its Printed Circuit Board, is old then it is vulnerable to deterioration which can lead to cracks and fractures in its internal structure. This damage over time can cause interruptions in the way your boiler is supposed to work, leading to a drop in its efficiency.

Damaged Solder Joints

by the nature of how it is made, the PCB has small electrical components that need to be soldered together. As the PCB ages, or is put under sustained pressure, this solder can deteriorate or snap off, causing a break in its working and ultimately resulting in a malfunction or full breakdown. While spot repairs are possible, it may be the best option to replace the PCB with a new unit.

Boiler Age

the final main cause of a PCB fault or full breakdown is your boiler itself, and how old it is. With so many delicate electrical components and moving parts, a boiler is inevitably prone to wear and tear over time, reducing its ability to function as efficiently as it should. Eventually parts will break down and become damaged or unusable, including the brains of the whole operation, the Printed Circuit Board. So, if your boiler is 10 years or older and is showing signs of age and deterioration, it may be time for an upgrade to a new boiler system.

The Cost of Repairing Your Boiler’s PCB

A PCB fault will need to be addressed and as an essential element of your boiler and central heating system, along with the heat exchanger, it is also one of the most expensive parts to replace. If your engineer is unable to repair the PCB, your next option is to have a replacement PCB installed. Depending on the make and model of your boiler, you can expect to pay around £500 for a new PCB, plus the added heating engineer costs of it having it installed.

When considering the cost, your first course of action is your warranty. However, PCB failures are more common on older boiler models which are likely to be out of warranty so do speak to your heating engineer. On balance, it may be a more cost-effective option to have a new boiler installed rather than a replacement PCB which should save you money in the long run.

How Long Does a PCB Take To Fit?

If the PCB fault cannot be repaired and you opt to replace your boiler’s Printed Circuit Board, then it will typically take two to three hours to fit a new one. However, it is important to always take advice from your heating engineer as to the best solution for your boiler and heating system. With an old boiler (10 years or more) it may be more cost-effective in the long run to replace your old system with a brand new boiler. And this is because if you are experiencing faults with your PCB, there’s a good chance that other electronic components in your boiler are also starting to deteriorate. And with any boiler, your objective is to have consistent, efficient and cost-effective heat, hot water and all-round comfort in your home.