Blog>Expert Advice>Common Vaillant boiler problems: troubleshooting tips and when to call a professional
Last updated: 19 November 2024
Common Vaillant boiler problems: troubleshooting tips and when to call a professional
Vaillant boilers are known for their reliability but they can still experience problems from time to time. Here’s all you need to know.
Vaillant boilers are a favourite amongst homeowners, thanks to their efficiency, performance and reliability. But like any boiler, they can still experience boiler faults from time to time.
Here, we’ll explore the most common Vaillant boiler problems and walk you through some troubleshooting steps.
Common Vaillant boiler problems
From error codes to no hot water, here are some of the main problems you might come across with your Vaillant boiler.
Vaillant boiler producing hot water but no heat
Noticed that your Vaillant boiler is producing hot water but no heat? This could be due to a fault with your boiler, but it could just as easily be a case of incorrect settings or even air trapped in your radiators.
Here’s what to check.
1. Combi boiler settings
If you have a combi boiler, check the settings. It might have accidentally been set to only heat water and not the central heating.
2. Radiators
If your radiators aren’t heating up, this could be because of air trapped within them, rather than a problem with the boiler itself. Try bleeding the radiators to release any trapped air.
3. Faulty boiler or heating system
If your central heating system still won’t turn on, this may indicate that there’s a fault with your boiler or heating system.
A Gas Safe registered engineer near you will be able to diagnose the fault and get your central heating back up and running.
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Vaillant boiler not producing hot water or heating
Have you been left with no heating or hot water? This could be down to all sorts of problems, from thermistor issues to a faulty diverter valve.
With that in mind, it’s normally best to call in a Gas Safe registered engineer to diagnose the issue.
That said, there are a couple of checks you could carry out yourself first.
1. Boiler connection
First things first, check that your boiler is connected to the power supply. You never know, the connection may have been switched off accidentally, or during a power outage.
2. Frozen condensate pipe
If temperatures outside are freezing and you have no heat or hot water, this could be due to a frozen condensate pipe. Normally, you’ll get an error code to confirm this, or you may also be able to see visible ice formation.
You can dislodge and melt the ice blockage by simply pouring warm water along the affected area.
3. Boiler pressure
Check the boiler display panel to see if the pressure level is too low or high – usually, it should be around 1.5 bars, although this can vary a little depending on your boiler model.
If the pressure reading isn’t where it should be, the system can turn off automatically, leaving you with no heating or hot water. Which brings us onto…
Vaillant boiler losing pressure
Low boiler pressure can lead to issues like no hot water and cold radiators. So, it’s an issue you’ll want to deal with quickly.
1. Leaks
If you spot that your boiler pressure has dropped suddenly, there could be a major leak in the system. This is a serious issue and should be dealt with as soon as possible by a qualified heating engineer.
2. Repressurising
Alternatively, your boiler pressure may have dropped if you’ve recently bled your radiators. If this is the case or you notice the pressure has dropped gradually, you may be able to resolve the issue by repressurising the system.
This involves topping up the water in your central heating system so that it can function properly again.
Vaillant boiler showing error codes
Is your Vaillant boiler showing an error code? This can be really helpful, as your boiler is essentially telling you what the problem is!
Here are some of the most common Vaillant boiler error codes and what they typically mean.
1. F22
The error code F22 indicates low water pressure. If your boiler’s water pressure has dropped suddenly, this can be a sign of a major leak, which will need immediate attention from a professional.
However, if the pressure has dropped gradually, you may be able to fix the issue yourself by repressurising the system.
2. F27
If your Vaillant boiler displays the error code F27, this could either be because of a defective flame sensor, or because of a faulty gas valve or printed circuit board (PCB).
You’ll need a Gas Safe registered engineer to diagnose the issue.
3. F28/F29
This error code is caused by a boiler lockout that stops access to heating or hot water.
It can be linked to several different issues, including:
Gas valve settings
The ignition unit or ignition leads
The air inlet duct
A Gas Safe registered engineer will be able to diagnose and fix the issue for you.
4. F75
The F75 error code is normally caused by a faulty heating pump or pressure sensor. A Gas Safe registered engineer will be able to fix the issue for you with replacement parts.
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Vaillant boiler making unusual noises
Have you noticed your boiler making unusual noises? There are lots of different noises your boiler can make – and identifying the type of sound is often key to diagnosing the issue.
1. Kettling noises
If you notice your boiler is making a whistling sound like a kettle, this is known as kettling. It normally occurs when water is heated too quickly and can be caused by limescale buildup or a faulty component.
A Gas Safe registered engineer will be able to determine the cause for you.
2. Gurgling noises
If your boiler is making gurgling noises, this is a sign that air is trapped inside the system. You should be able to resolve the issue easily by simply bleeding your radiators.
3. Whooshing noises
If your boiler makes whoosing noises, check to see if there are any objects or debris blocking the air intake pipe that leads from the back of your boiler to the outside of your property.
If not, the cause if likely an air filter blockage, which will need to be resolved by a Gas Safe registered engineer.
4. Humming noises
Humming noises can be caused by water arriving from the mains at a pressure that’s too high. Alternatively, the issue could be related to a faulty pump.
Either way, humming noises should always be investigated by a qualified heating engineer.
Vaillant boiler pilot light keeps going out
Older boilers often have a pilot light that needs to be constantly lit to light the larger boiler burner. If this won’t light, your boiler won’t work.
1. Check your other gas appliances
If your other gas appliances aren’t working either, this indicates that there’s an issue with the gas supply itself – rather than with your boiler.
2. Faulty parts
Over time, the parts responsible for lighting the pilot switch can become faulty. If your other gas appliances are working correctly, this is probably what’s wrong.
Never try to fix the issue yourself, as it’s illegal to remove the boiler casing unless you’re Gas Safe registered. Instead, always enlist the help of a qualified professional.
How to reset your Vaillant boiler
If your boiler notices a fault, it will shut itself down automatically as a safety precaution. This is known as a lockout.
In this case, once the fault has been fixed, you’ll need to reset your boiler to get your heating and hot water back again.
It’s always best to check your Vaillant boiler manual to find out how to do this, as different models can have slightly different instructions.
However, here’s what the process usually looks like:
Locate the boiler reset button (normally, it will have a flame with a line crossed through it)
Press and hold the reset button for three seconds
Check whether the flame has ignited or the error code has disappeared
Just remember that your boiler won’t usually shut down without a valid reason.
So, always make sure you get to the bottom of it before resetting your boiler.
While you may be able to deal with a few minor issues yourself – such as a frozen condensate pipe or bleeding your radiators – most issues will need the help of a Gas Safe registered engineer. Which brings us onto…
When to call a professional
Unless you’re fully confident and sure of what you’re doing, it’s always best to call in a professional.
Yes, there are a few small fixes that you can try yourself – like bleeding your radiators, unfreezing a condensate pipe or repressurising your boiler.
But in almost all cases, calling in a professional is the best way forward.
Not only do they have the skills, knowledge and experience needed to diagnose the problem and find a fix as fast as possible. But it’s also illegal to carry out work on a gas boiler without being Gas Safe registered.
This is because working with gas can be very dangerous if you don’t know what you’re doing.
Ultimately, calling in a professional for boiler repairs is always the best option, both for your safety and peace of mind.
Find a trusted professional for boiler repairs
If your Vaillant boiler isn’t working as it should be, you’ll want to get the issue fixed sooner rather than later.
Luckily, you’re in the right place.
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