8 Common Ariston Boiler Problems And How To Fix Them

If you have a problem with your Ariston boiler, this is the guide for you. Take five minutes now to read about the 8 most common problems with Ariston boilers and you could save yourself a ton of money on unnecessary engineers fees. This guide covers the majority of Ariston boiler issues and also offers the best advice on how to fix them.

“And on, and on, and on, and on, and Ariston”, the famous old advert used to say, and it’s true. Ariston boilers still have a reputation for being durable and long-lasting. But that doesn’t mean they never go wrong.

Like all boilers, Ariston ones can go wrong from time to time and when they do, it can be extremely frustrating for customers.

While there are lots of possible causes of boiler issues, many stem from the same few causes and these can often be resolved quite easily. Other issues will be more severe and could require a major repair or even a new boiler.

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In this guide, we will outline the 8 most common problems with Ariston boilers, what is causing them, and how you can fix it. Where necessary, we will also recommend which faults might mean you should consider buying a whole new boiler.


The 8 Most Common Ariston Boiler Problems

#1 – Low Water Pressure

Low water pressure is a common issue with many boilers and Ariston ones are no different. If you do have low water pressure in your boiler, you are likely to see error code 108 on your boiler display panel.

The most common cause of low water pressure is a leak. This leak could be somewhere in your boiler but it could also be anywhere else in your central heating system too.

How to Fix it:

Repressurising a boiler is easy. Anyone can use the external filling loop to increase pressure in the system to around 1.3 bar, which is the pressure required in most Ariston boilers. This will clear the error code and get your boiler working again.

However, if the loss of pressure is caused by a leak, it is only a matter of time before the pressure drops again.

To solve the problem permanently, you will need to locate the leak and fix it. This can sometimes be done yourself. Check all your exposed pipework, radiators, towel rails, and boiler pipes for evidence of a leak. If you find something, you should be able to fix it using a DIY kit by tightening any loose joints or connections.

If you can’t identify the source of the leak or are unable to fix it, you will need to contact a qualified engineer. They will check your system themselves and fix any problems they find.

#2 – No Pilot Light

When the pilot light goes out on an Ariston boiler, the display panel is most likely to show error code 501.

There are several things that can cause a pilot light to go out or refuse to light. By some way, the most common problem with Ariston boilers is a blockage in the pilot jet. This stops the gas reaching the pilot light efficiently and so causes the pilot light to extinguish.

In some cases, you will see a 501 error code but the pilot light will still be lit. When this happens, it is likely that your flame sensor has developed a problem.

How to Fix it:

As this is a problem that is related to your gas supply, you will want to get a qualified engineer to fix this one for you.

If the pilot light is blocked, they should be able to clear it out and reinstall it. In a few cases, they might need to replace the pilot jet, but this is a fairly minor issue and shouldn’t cost too much.

Your engineer should also check for anything else that could be affecting the pilot light ignition too and also test the sensor. If there are any other issues, they will be able to recommend the appropriate fix.

#3 – Air Pressure Switch Fault

A boiler’s air pressure switch is the component which helps to ensure that all the harmful gasses created by your boiler are pushed up the flue pipe and outside your property.

If there is a problem with this component and the boiler things it can’t expel these gasses, this is potentially very dangerous and your boiler will trigger a failsafe and lockout if it thinks there is a problem.

On most Ariston boilers, this will trigger an E34 error code, although some models may have a different code.

How to Fix it:

If the problem is limited to the air pressure switch, this is something that your engineer should be able to fix relatively affordably and easily.

But another possible cause of this fault code is a problem with the connection between your boiler’s printed circuit board (PCB) and the air pressure switch, This is a much bigger issue and could mean your boiler needs a new PCB.

This is extremely pricy and in older models could mean you are better buying a brand new boiler.

#4 – Broken Fan

The fan inside your boiler is another critical component that helps to expel the noxious gasses created inside. If the fan isn’t working, your boiler cannot vent these gasses out through the flue and again your boiler will lockout as a failsafe measure.

If this is the problem, you are likely to see error code A41 on most Ariston boilers.

How to Fix it:

This is another issue where you will need the help of a qualified engineer. They will be able to take your boiler apart, assess the fan and see whether it is blocked or damaged.

If you need a new fan, this can be replaced without a huge amount of expense. But in our experience, if the fan has gone, other major components are likely to be on their lasts legs too and if your boiler is an older model, it might be time to invest in an upgrade.

#5 – Fan Running too Slow

One problem with your fan that might not be such a big problem is if your boiler fan is running too slowly.

This will mean it is unable to push enough gasses out of your boiler and is therefore likely to lead to a lockout.

But, it is more likely that a blockage or lose component is causing the issue and this is usually easier to resolve.

If this is the problem with your boiler, you are most likely to see error code 604 on your display screen.

How to Fix it:

As with the previous problem, this fan issue will require a qualified engineer to take a look at your boiler. They will be able to clear out any blockage and tackle any loose components as well as check to ensure that the fan and other relevant parts are functioning properly.

#6 – Faulty Printed Circuit Board

If there is a problem with your boilers Printed Circuit Board (PCB), this is a major and potential very experience issue.

The PCB is the key component in your boiler that helps everything communicate. If it is not working properly, it is likely that your whole boiler will stop working.

There are a whole host of different error codes which can (but don’t necessarily always) indicate a problem with your PCB. These include 301, 302, 303, 304, 305, 306, and 307.

The main PCB errors are 303, 305, 306, and 307. If your boiler is showing one of these, there is a reasonable chance you might need a new PCB.

How to Fix it:

There is no DIY fix for a PCB issue. You will need to get a qualified engineer to assess your boiler and run various diagnostic tests to determine the cause of the problem.

If they determine that you need a new PCB, you are looking at a cost of at least £500 to replace it.

If you have an old boiler that is out of warranty, our recommendation would be to buy a replacement boiler rather than this single part.

If you buy from a site like Heatable, you are likely to only need to pay around £1,675 for a brand-new energy efficient boiler that will have a long warranty and shouldn’t cost you any more money for a very long time.

#7 – Ignition Fault

Another common issue with Ariston boilers is an ignition fault. These usually result in error codes 5P1 or 5P2 showing up on your display panel.

Problems with your boilers ignition can be caused by a number of different things. It could be a blocked burner or debris that is affecting either the burner or the pilot light. There could be an issue with the ignition leads or probe, or perhaps the spark generator isn’t working properly.

How to Fix it:

You will need to get a qualified engineer out to fix this issue but often a clean and service will be sufficient to clear any debris or blockages and get the ignition working again.

It is possible that the ignition component itself might be damaged and need replacing. This piece alone is simple and fairly affordable to replace. But if this is what your engineer recommends, it is worth asking him to check the state of your boilers other main components as a failing ignition can sometimes indicate that other parts are on their last legs too.

If this is the case, a new boiler might be your best course of action.

#8 – Lack of circulation

If there is a problem with your Ariston boilers central heating pump or a blockage in your heating system, this can result in a lack of water circulating around the system and your radiators and towel rails not reaching a sufficiently warm temperature.

Possible problems with your central heating pump include blown seals, airlocks, worn-out bearings or pump shaft, incorrect speed settings, or even incorrect installation.

Any blockages in your system are likely to be caused by a build-up of sludge either in the boiler, the pipework, or the radiators. If you live in a hard water area, it is possible that limescale build-up is causing the problem too.

These problems are usually indicated on an Ariston boiler with any error code between 103 and 108.

How to Fix it:

If you think the problem stems from your central heating pump, you will need an engineer to take a look. They will be able to replace any worn or deteriorating parts or recommend a new pump is installed.

If the pump is making a noise, an airlock could well be the cause and you can release this yourself using the bleed key on the front of the pump which should be located just behind your boiler’s casing.

Should the problem stem from a build-up of either sludge or limescale, you will need an engineer to run a hot flush which clears the sludge out of your system. You should also ask them to install a magnetic filter which can help stop similar build-ups occurring in the future.

Resetting An Ariston Boiler

Once your problem has been resolved, you will then need to reset your Ariston boiler.

To do this, first check that any error code or flashing lights have disappeared from the display panel. If they haven’t you will need to consult with an engineer.

Different Ariston boilers have different reset methods, so if there is no obvious reset button on your boiler, consult your manual to find out the reset method.

Buying a new boiler

If your Ariston boiler has a major fault and is already old and out of warranty, you are likely to be best to buy a whole new boiler.

If you do decide to go down this route, it is advisable to get multiple quotes before making a decision. When you do, be sure to get a quote from Heatable.

Heatable is an online installation company that offers some of the lowest prices around on a wide range of boilers from all the top manufacturers. They have some great offers and special deals such as extended warranties available too.

Just visit their website and fill in their short form. You won’t have to share any personal information and they will give you a fixed-price quote on the best new boiler to suit your property.


Ariston boilers really do go on and on, but even the best can break down or develop faults sometimes.

In this guide, we have identified the 8 most common issues with Ariston boilers and explained how to fix them.

We have also suggested some occasions when you might want to consider buying a new boiler instead and recommend Heatable as the best place to find a cheap quote.

Have you had any problems with your Ariston boiler? Do you have any questions or tips for our readers? We always love to hear the comments and questions of our readers, so please do share yours with us using the comment box below.

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