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Common Vaillant boiler problems & fixes


27 November 2020

At Homecure we’ve been providing installation, repairs and boiler servicing for Vaillant boilers for a number years, with our Gas Safe engineers able to deal with any issue you are experiencing. This has enabled us to build up years of knowledge and experience to provide solutions to all kinds of Vaillant boiler problems.

In many cases a Vaillant boiler with water pressure problems is a common reason for a breakdown, faulty pumps and gas valves or frozen condensate pipes. Even in situations where an error code is displayed that is not so common we understand how to apply a suitable fix.

There are some instances where you may be able to resolve the problem without calling an engineer, which we explain in more detail below. However, for those that require part changes, internal boiler checks or anything requiring technical expertise, you should always get in touch with a qualified engineer.

Read through our list of common breakdowns and fixes below to learn more about what to do when Vaillant boilers need troubleshooting and what to do next time you experience a fault.

Top 10 Vaillant Boiler Problems

1. Low water pressure

When you see a Vaillant boiler F22 error code this means water pressure is low in the system. A Vaillant boiler with low water pressure can usually be fixed by opening the external filling loop to raise the pressure back to 1.5. Often seen on an ecoTEC plus 428 with problems. If you own a this sort of model, use the built-in filling loop instead, as detailed in the manual.

2. Faulty pressure sensor or pump

Vaillant ecoTEC boilers are known for displaying the F75 code which means the system cannot find the right amount of pressure while the pump is working. This would require one of our team to visit to check whether it is the pump or pressure sensor that needs to be fixed.

3. Failed ignition

Vaillant boiler problems with no hot water or heating is quite common, which will produce a Vaillant F29 error warning. It can be the result of a frozen condensate pipe, lack of gas supply or defective spark electrodes. This is a common issue Homecure engineers are able to diagnose and resolve. A Vaillant F28 error code also related to the same issue.  

4. Incorrect flame detection

If the gas supply and ignition aren’t deemed as being safe the boiler may show up a Vaillant f27 error warning, which will lead to a lockout. You will need to contact a professional Gas Safe engineer who can provide boiler repairs to fix this issue, which could be associated with moisture in the electrical parts, worn down ignition leads or a faulty printed circuit board.

5. Frozen condensate pipe

A frozen condensate pipe can create a number of problems on different Vaillant boilers. If this is the cause you can usually fix this yourself by thawing it out with warm water. However, if you do not feel confident taking this sort of action, the Homecure team are always available to help.

6. Slow flow rate

Sometimes you may experience a slow rate of water coming out of taps and shower heads in the home. This problem may be related to the pump, the height position of your water tanks or be linked with an open-vent heating system.

7. Faulty gas valve

If the gas valve has become stuck it could create a dangerous situation that leaves the supply running instead of being closed off after the hot water or heating has been turned off. This displays the F62 and will require a Gas Safe engineer to attend – a task the Homecure will be able to assist with.

8. Over activity

A Vaillant ecoTEC Plus 832 with problems related to over activity could be caused by a faulty thermostat or temperature settings. If you find it is firing up unexpectedly during the day, check the temperature levels against the time period to avoid it becoming active when you don’t want it to. The Vaillant ecoTEC Plus 831 had problems similar to this, but this model has now been discontinued.

9. Sensor faults

If you experience either a F52 or F53 fault code this indicates an issue with the mass flow sensor. On Vaillant ecoTEC boilers these are located just behind the gas valve and are connected to the fan. This will require an engineer to conduct an electrical test to verity the issue and install a replacement if needed.

10. Unstable flame

A Vaillant boiler producing the F68 error code means the flame is unstable which could be caused by a number of reasons. This includes the gas flow pressure being too low, a frozen condensate pipe or air being present in gas. One of our qualified team members can resolve this quickly and safely.

Which Vaillant boiler problems need a Homecure engineer?

Vaillant boiler repairs can be the result of a number of different issues. The table below describes the most common reasons for a breakdown and whether or not you will need to call out a Homecure engineer.

Boiler issue

Possible reason

Should I call a Homecure engineer?

Banging noises or whistling

This is usually caused by air in the system or by low water pressure leading to kettling.


Frozen condensate pipe

This will produce an error code on the boiler warning you of the problem.

Maybe – you can try to defrost the pipe using warm water but if that doesn’t work you should give us a call.

No heating or hot water

There can be a number of reasons for this, either to do with valves, water levels or thermostat issues.



Leaks are typically the result of a broken piece of equipment and may not always be externally visible


Low pressure

May be caused by a leak, faulty valves or radiators that need to be bled.

Can usually be fixed at home by using the filling loop, but if not, give us a call.

Problems with thermostat

This may be related to current timings and settings.

Yes – it may need to be replaced if this does not resolve the issue

Boiler shutting down

May be the result of a faulty thermostat, low water pressure, low water flow or faulty air pump


No pilot light

A broken thermocouple could be the cause for this.


Cold radiators

Radiators not heating up when turned on could be caused by a build-up of air or sludge in the system.

You can bleed the radiators with a key – if this doesn’t fix the issue, or you aren’t comfortable doing it, call our team.

Kettling noises

Caused by a build-up of sludge or air in the heat exchanger.


Our team at Homecure offers a range of services across a number of other brands, including boiler repairs for Worcester, Glow Worm and Baxi.

Vaillant boiler error codes

There are a long list of Vaillant error codes and below we explain some of the most common to help you understand what they mean and how they can be fixed.

Error Code



This relates to a lack of water or pressure and can be fixed by opening the filling loop to return the pressure level back to 1.5.


Can be caused by a faulty gas valve or printed circuit board (PCB), or a defective flame sensor. An engineer can diagnose the issue, although if related to the PCB, a new boiler installation may be cheaper.

F28 & F29

Caused by a boiler lockout which stops access to heating and/or hot water. Can be linked to the gas valve settings, the condition of the ignition unit or ignition leads, or the air inlet duct.


A Vaillant ecoTEC Pro 28 with problems usually displays this code, caused by a faulty heating pump or pressure sensor or sometimes both. This can be fixed with part replacements.


May be a result of a jammed gas valve or faulty communication between the PCB and gas valve. An engineer will check to diagnose the fault.


This will display when the boiler overheats due to low water pressure. Opening the filling loop so the pressure level can go back to 1.5 should fix this.


Issues with the fan or flue tend to be the cause of this error code displaying. The flue can be unblocked by an engineer, or they can replace the fan, if needed.


A faulty gas valve is likely to produce this Vaillant error code. This will be different to an incorrectly adjusted valve and can be replaced by an engineer.


The F63 error code will be linked to the PCB, which will require an engineer to use a multi-meter to determine the exact cause of the issue.


If the flame is either constantly weak or keeps going out it will produce this code. An engineer can diagnose if it is down to a blocked flue, faulty fan or air pressure switch or an incorrectly adjusted gas valve.


FAQs about Vaillant boiler problems

What is wrong with my Vaillant boiler?

The best way to find out what is wrong with your Vaillant boiler is to cross check the error code with the user manual. Sometimes you can resolve the issue yourself, however, if you see an F60 error on a Vaillant Turbomax Plus 824/828E system this means a gas valve control is defective and requires a qualified engineer to fix it.

How do I reset my Vaillant boiler?

There are a number of reasons you may want to reset your Vaillant boiler, if it is locked out for example, and it’s an easy process to complete. Press and hold the reset button for a couple of seconds which should get things back to normal. If not, one of our engineers will be able to help.

Why is my Vaillant boiler losing pressure?

Low pressure can be caused by a leak, or if a Vaillant boiler service is pending, it may just require a reset. If the F22 boiler error code is showing this means there is a leak in the system. Our Vaillant engineers can quickly identify and fix this issue to have the boiler up and running and again in no time.

How long should a Vaillant boiler last?

A standard Vaillant warranty lasts between 2-5 years. This can be extended up to 10 years in some cases. If the boiler is serviced regularly and kept in good condition it could last for at least 15 years.

Why does my Vaillant boiler keep turning off?

There can be a number of reasons why your Vaillant boiler keeps turning off. It could be due to low water pressure, a faulty thermostat, a faulty water pump, air in the system or frozen condensate pipes. One of our engineers will be able to find the issue and quickly apply a solution for you.

How do I turn on the heating on my Vaillant boiler?

How you turn the heating on with a Vaillant boiler may differ slightly depending on the model. The manual will be able to offer clear, easy-to-follow instructions. For a Vaillant ecoTEC pro combination boiler, use the on/off control to move it from ‘0’ to ‘I’.

How do you reset a Vaillant ecoTEC boiler?

To rest a Vaillant ecoTEC boiler, press and hold the reset button for one or two seconds. If this doesn’t reignite the boiler, try resetting the ecoTEC boiler three times. In the event this doesn’t resolve the issue, contact a qualified Gas Safe engineer who will be able to help.


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