Boiler PCB Fault Finding and PCB Board Cost to Replace

Welcome to our 5-minute guide to boiler PCB faults — this is all the info you’ll need if your boiler’s printed circuit board (PCB) is malfunctioning.

Since printed circuit boards function much the same way in every boiler, our guide works for any appliance — from the old Potterton Suprima, to the Ideal Isar, to, of course the newer Worcester Greenstars.

What does PCB stand for?

PCB stands for “Printed Circuit Board”. It’s a laminated board with electrical conductors, which is essentially a control centre that facilitates communication between various electronic components of a device. PCBs are used in a vast array of electronic devices, including boilers.

What is a PCB on a boiler?

A boiler’s PCB is the brain of all electronic components, which communicate through it.

For example, the air pressure switch may send a signal to the PCB that the fan is operational (helping to vent gases out the flue), and therefore it’s safe to ignite the boiler.

Likewise, NTC thermistors communicate via the PCB to tell the boiler whether the difference in temperature between the flow and return pipes is within working range.

A boiler circuit board also monitors pressure, temperature, and currents, to ensure that the boiler is:

• Working in a way that won’t damage internal parts
• Isn’t posing a safety threat to its users

Symptoms of a Faulty PCB

Before we go any further — unless you’re Gas Safe-registered, you shouldn’t be opening a boiler’s casing or working on a boiler circuit board. Contact a Gas Safe heating engineer right away if you suspect any internal fault with your boiler.

Now, let’s have a look at some common symptoms pointing to a PCB problem.

#1 – Intermittent Display Panel Operation

The boiler circuit board interconnects with all electrical components on your boiler, including the display panel. If you see lights (green, red and blue, depending on your boiler) flickering, this can be a sign of a faulty PCB.

However, don’t confuse this with flashing — some boilers use flashing as a signal they are in service, or have a fault.

#2 – Burning Smell Coming From Boiler

Burning smell from a boiler that operates sporadically, or has a display panel failure, can mean parts of the circuit board have burnt out.

#3 – No Power On Display Panel

If there’s no power to the display panel, the boiler PCB could be at fault. The engineer will need to test this by checking whether the PCB has power.

If it does, they’ll then move onto other parts, like the fan, to determine whether the issue lies with the PCB or other parts in the boiler.

#4 – Boiler Operates Sporadically

Since the boiler’s PCB effectively controls all internal electrical components, when it fails, they can malfunction.

The PCB may miscommunicate with things like the programmer, causing the boiler to cycle on and off. Or, it may relay the wrong signal from the air pressure switch, and the boiler won’t fire up.

Note that these symptoms can easily be misdiagnosed, as most aren’t limited to one faulty part. For example, a display panel failure could be a boiler circuit board issue, OR an electrical supply issue. Likewise, a malfunctioning fan could point to a boiler PCB problem, but it could just as easily be the fan itself.

Fault Finding With a Boiler PCB

Fault finding isn’t always easily — there’s a tonne of the things that can cause your boiler circuit board to fail.

The best course of action is to have an engineer come and run some electrical tests using a multimeter on your boiler.

To determine the cause, they might look for any of the following.

#1 – Leaking Boiler

Whether it’s a small leak from the pump, or a cracked heat exchanger, water is the killer of boilers’ electrical components. Inside the boiler, moisture can cause a wiring issue and find its way into electrical components, like the ignition lead and of course, the PCB.

If there are leaks present in the boiler, your engineer needs to find and fix them before replacing the circuit board.

Note that leaks may occur anywhere in the central heating system, not just the boiler itself. And whilst a leaky radiator has no effect on the well-being of your PCB, it’s still wise to fix such a leak as soon as possible to avert property damage and boiler pressure issues.

#2 – Cracks And Fractures

Cracks and fractures on the PCB will cause it to malfunction. If it shows signs of either, it’s probably time for a replacement.

#3 – Weak Or Damaged Soldered 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, given the time it will take, it’s much wiser to replace the whole unit.

If you’re not prepared to sink £300-550 into an old and unreliable boiler, you can get a replacement price right now by filling in a 90-second, anonymous form at Heatable. They’re always running promos on top boiler brands, so if it’s a new Worcester boiler you want, this is about the cheapest place to get one.

PCB Repair Costs

Circuit board repair is rarely worth it — it makes far more sense to get a replacement PCB.

And if your boiler is out of warranty and in need of frequent repairs, you should think about getting a new boiler instead.

The time spent on boiler repairs (and therefore the cost of labour) usually gets close to the cost of the replacement part anyway.

The Cost to Replace a Boiler’s PCB

Labour rates vary across the country, and so do the prices of boiler parts.

But, you can expect to pay anywhere between £300-550 for a replacement PCB unless you’re protected by a boiler cover policy.

This price drops if you’re considering a refurbished or reconditioned unit, but again, it’s rarely worth the small cash saving to have a second-hand unit (that has no warranty).

Should You Replace Your Boiler?

If your boiler is out of warranty and starting to show it’s age, there’s little point investing upwards of £300 in it — a fitting a new boiler is the wiser investment.

There’s a good chance other expensive parts are going to let go in the not-so-distant future.

It’s worth weighing up the cost difference between repair and a replacement when the engineer arrives. Or, you can check the exact price you’ll pay for a Worcester Bosch installation here.

How Long Does a PCB Take To Fit?

Depending on the complexity of the boiler, it should take 2-3 hours for a diagnostic and fitting.

Other Common Boiler Faults

A boiler PCB failure isn’t the only error you may encounter. Boilers have numerous moving parts, and when one of them malfunctions, each boiler brand typically has a unique fault code that alerts you to the problem. Check out our knowledge base below to learn more about:

• Vaillant faults
• Ideal faults
• Worcester faults
• Vokera faults
• Alpha faults
• Viessmann faults
• Glow Worm faults
• Baxi faults

Of course, if you’re fed up with a never-ending torrent of problems (and pricey fixes) it may be time to consider replacing your faulty boiler. Fill out this quick, anonymous questionnaire from Heatable and get fixed prices on a range of models from the best boiler brands in the UK (there’s one for every budget).

FAQs About PCB Faults On a Boiler

Before we conclude, we’d like to answer a few questions that we often hear about PCB fault finding on boilers.

How long does it take to replace a boiler’s PCB?

Once the Gas Safe engineer gets to work, it should take them anywhere between 1-3 hours to replace a PCB. The duration of the procedure hinges on the complexity of the issue. For instance, if the PCB and the surrounding wiring have sustained water damage, it may take longer to replace the faulty component.

Another factor to consider is how long you’ll have to wait for a heating engineer to show up at your home; it may be difficult to get same-day service.

Can you change a PCB on a boiler?

Yes — you can change a boiler’s faulty PCB. Often, however, the question is whether such a replacement is worth it.

For instance, if your boiler is still new, otherwise healthy, and under warranty, PCB replacement is certainly the right way to go.

However, if your appliance is old, no longer covered by a warranty, and breaks down often, then sinking £300-£550 into a new PCB may not be worth it — something else will kill your boiler sooner rather than later anyway. In this case, it may be wise to get a new boiler instead.

How much is a PCB board?

A PCB on a boiler can cost anywhere between £300-£550 to replace. That’s including the component itself, as well as the cost installation by a Gas Safe engineer.

How is a PCB fault diagnosed?

There are certain symptoms that may point to a faulty PCB. Note that these cannot give you a diagnosis that’s 100% correct, so it’s always wise to hire a boiler engineer to inspect your appliance if you suspect a PCB error.

Can a PCB be repaired?

In theory, yes, it’s possible to repair a PCB that hasn’t completely failed. The Gas Safe engineer inspecting your boiler will be able to determine whether repairs are appropriate.

However, in most cases, it makes more sense to get the PCB (or even the boiler itself) replaced.

What’s Next?

We hope this guide to boiler PCB faults will help you fix the problem and get your boiler humming along in no time.

If there’s anything we didn’t cover, or you have a question or an experience to share, please leave our readers and us a comment below!