Boiler PCB Faulty? What Is a PCB on a Boiler, How You Fix It

The Printed Circuit Board (PCB) in your boiler is the motherboard of your hot water and central heating system. And if it goes wrong, you could be looking at a huge bill to fix it. In this guide, we are going to tell you about some of the most common PCB faults and how you can fix them.

Every boiler is built around its PCB and no matter what make or model you have, this component is crucial to keeping it working properly.

But if it goes wrong, it can be a major issue and wind up costing you hundreds of pounds to fix.

In this guide, we will discuss some of the most common problems that can crop up with your printed circuit board in more detail. We will explain where these problems can be fixed quite easily and where it is a bigger job.

And we will also explain when you would be better off investing in a whole new boiler from a site like WARMZILLA than paying out to fix your old PCB.


Spotting A Faulty PCB

Before we delve into the detail of PCB problems, it is important to stress that the PCB is literally as well as figuratively at the heart of your boiler. It is a component that you should not mess around with yourself, so no matter what the issue is, we strongly recommend you call out a qualified gas engineer to fix it.

It is also important to stress that because of the various crucial roles the PCB fulfils, it is quite easy to misdiagnose problems related to the PCB. If another component such as your boiler’s fan isn’t working properly, it is quite possible that the fault actually lies with the PCB rather than the fan.

Your engineer should be aware of this but it is worth ensuring that he has diagnosed the issue correctly before you shell out for expensive repairs that might possibly not be necessary.

In this section, we will detail some of the most common symptoms of a faulty PCB:

#1 – Burning Smell

If there is a burning smell coming from your boiler, this can mean parts of the circuit board have burnt out. This is a serious issue and will cause your boiler to lockout completely.

Fixing a burnt-out circuit board will require installing a new one. This fix is extremely expensive and if your boiler is old and out of warranty you are probably better off buying a new one.

#2 – Display Panel Operation Intermittent

If the display panel on your boiler is only working intermittently and you see lights, which could be either green, red, or blue, flickering on it, it could be a sign of a faulty PCB.

But be aware that flashing lights can mean other things too depending on the make and model of boiler you have, so don’t leap to any conclusions.

#3 – No Power On Display Panel

If there’s no power on the display panel at all, it is also possible that the PCB could be at fault.

You will need to get an engineer to test this by checking the PCB has power. This diagnosis is a big job and might involve taking other parts of your boiler apart.

With luck, it will be a wiring issue which is relatively simple to fit. If not, you could need a new PCB which, as we have already said, is an expensive job.

#4 – Sporadic Operation

The PCB manages all the internal electrical components in your boiler and if it develops a problem, it can cause these to malfunction. You will most likely notice this by sporadic performance in your boiler.

This can be as a result of miscommunication between the PCB and the programmer or the air pressure switch.You will need a qualified engineer to determine the precise nature of this issue.

What Your Engineer Will Be Looking For

You will need to get an engineer to take a look at your boiler and run some test to diagnose if there is an issue with your PCB.

When the engineer pays a visit, there are a number of things that they are likely to be on the lookout for including:

#1 – Leaks

Electricity and water do not go well together and if water has got onto your PCB it is quite likely to do some serious damage.

Your engineer will, therefore, be looking for evidence of leaks within your boiler. These are most commonly from either the central heating pump or a crack in the heat exchanger.

Any water that leaks is likely to condense and then find its way onto your electrical components.

If your boiler does have any leaks, these will need to be fixed before your PCB is attended to and replacing things like the pump or the heat exchanger is a big and expensive job on its own.

#2 – Cracks

If your PCB is old, there is a chance that it can begin to deteriorate and cracks or fractures can appear in it.

This will cause it to stop working or to only work intermittently.

Your engineer should be able to spot this fairly easily, but unfortunately, it will mean that you need to invest in either a brand new PCB or a whole new boiler.

#3 – Weak Or Damaged Soldering On Joints

The small electronic components that make up your circuit board are soldered together. If this solder deteriorates, breaks off, or gets damaged, the unit will malfunction.

Of course, there is an option to spot weld to repair the PCB. But, the time it takes means it’s much wiser to replace the whole unit.

The cost of repairing your Boiler’s PCB

PCB’s are one of the most expensive components to fix in a boiler.

Costs will vary from one make and model to another, but typically you can expect to pay at least £500 to replace a PCB. If you are willing to opt for a reconditioned PCB, you can save money but the savings are minimal and you are accepting a second-hand component that can easily go wrong again quickly.

Our honest assessment is that unless your boiler is under warranty, it generally isn’t worth bothering spending such a huge sum to replace a PCB.

If you have an old boiler anyway, it is only a matter of time before another component needs replacing. If you have a new boiler and the PCB has blown, you are either very unlucky or have a very low-quality unit.

Either way, you are going to be better off spending a bit more money on a brand new energy-efficient boiler than patching up your existing one.

It’s worth weighing up the cost differential between a repair and a replacement with your engineer. Remember to factor in the utility savings you are likely to make from buying a new energy-efficient boiler.

How Long Does a PCB Take To Fit?

If you do decide to replace your PCB, the length of time the job will take depends on the make and model of boiler you have and also whether any other components need replacing.

Typically, it will take a qualified engineer 2-3 hours to diagnose and fit a new PCB.

Where to buy a new boiler from?

If you are going to buy a new boiler, you should always get a minimum of three quotes.

We would strongly recommend that at least one of these comes from WARMZILLA.

WARMZILLA is an online installation company that offers some of the lowest prices of a huge range of high-quality boilers from all the top manufacturers.

It has some terrific special deals too, including extended warranties. Installation costs are low too and you can get a brand new boiler installed as quickly as the following day.

Just pay a visit to their website and fill in their online form. It takes less than two minutes and you don’t have to share any personal information. They will offer some fixed price quotes for the best boilers for your property. We are confident you will be pleasantly surprised by how much you can save.


PCBs are essential boiler components and when they go wrong it is generally bad news.

PCB issues can be hard to diagnose and are sometimes caused by other problems. But if you PCB is on the blink, you are looking at a big bill. A replacement PCB will set you back at least £500.

If your boiler is old and out of warranty, you will probably be best to replace your boiler entirely. We have recommended that you get a quote from WARMZILLA, the online installation company that offers some of the best prices in the UK.

Have you had problems with your boiler’s PCB? Do you have any tips we haven’t covered in this guide? Perhaps you have a question we haven’t managed to answer? If so, please do share it with us using the comment box below. We always try to respond to everyone.

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