Vaillant is a leading manufacturer of heating technology in Europe. They provide a wide range of models. You can opt for a combi, regular or system boiler depending on the heating and hot water need of your property.

Vaillant boilers are a popular choice because of their many advantages. They are well-known for their excellent performance, high efficiency, and low energy consumption. Vaillant boilers come in a variety of models, some of which can even fit inside a kitchen cabinet.

Despite their numerous benefits, Vaillant boilers, like any other technology, can occasionally experience problems. The good news is that most issues can be easily repaired by a skilled gas boiler and heating specialist.

Here’s a quick troubleshooting guide that will look at some of the most common Vaillant boiler problems. We will explain what the various fault codes mean, what causes them, and how they can be resolved.

In case you have a problem and need Vaillant boiler repair in London be sure to find a reliable and certified specialist. Our professionals have the necessary knowledge and experience to safely and properly repair your boiler. It is best not to attempt the job on your own because it is fraught with danger.

Key takeaways:

  • Vaillant boilers are a popular choice because of their excellent performance, high efficiency, and low energy consumption.
  • Common Vaillant boiler problems include water leaks, low boiler pressure, no hot water or central heating, frozen condensate pipe, kettling noise, thermostat and boiler not communicating, pilot light not staying on, and boiler lockout.
  • The most common Vaillant boiler fault codes are F75, F22, F28, F33, F62, and F27.
  • Fixing these problems and fault codes often requires the assistance of a qualified Gas Safe Engineer.
  • If your Vaillant boiler is not working and no fault code is displayed, check the energy supply, reset the boiler, examine the thermostat, and contact a Gas Safe Engineer if none of these solutions works.

The Most Common Vaillant Boiler Problems

boiler engineer checking a boiler for leaks

Here you will find a list of Vaillant boiler breakdowns, as well as instructions on what to do if you encounter one.

Water leaks

Many reasons might be to blame for a boiler leak. It could happen due to corrosion, a faulty valve or pump, damaged water pipe connections and others. This issue frequently occurs in older boilers. However, it may sometimes happen with new devices due to not proper installation.

Water leaks can sometimes be dangerous as they may lead to damage to the electrical components within the boiler. Fortunately, it is normally easy to identify whether your boiler is leaking since it causes damp spots on the floors or walls. Whatever you experience such a problem make sure to switch off your boiler and contact a Vaillant boiler repair specialist.

Low boiler pressure

If your Vaillant boiler experience low pressure then it will probably display the F22 error code. But what might be the reason for this issue? Vaillant boilers, like all boilers, may lose pressure due to leaks. Another thing that may lead to such a problem is a faulty pressure sensor.

How low boiler pressure can be fixed? First, you may try to re-pressurise the device to allow more water to enter the system. If this does not fix the problem, seek the assistance of a qualified technician.

No hot water, no central heating

If you have no hot water or heating then your boiler will show F29, F20 or F25 fault code. What might be the reasons for such a breakdown? It could be caused by a boiler lockout or it might be due to a problem with the gas supply and ignition. In some cases, a frozen condensate pipe can cause a lack of hot water and heating production.

If you have no heating or hot water then it might be best to call a specialist to check the root cause of the problem and fix it.

Frozen condensate pipe

If the condensate pipe froze over, your boiler will probably display either F29 or F28 fault code. This issue frequently occurs during the winter time. Every condensing boiler has a pipe which is responsible for transporting waste water produced during the condensing process outside your home. When temperatures drop below zero, the water in the pipe freezes, which in turn causes the boiler to shut down.

Fortunately, this issue can be easily resolved. All you need is to pour some warm water over the pipe. It will help melt the frozen water and get your pipe running again.

Kettling noise in the boiler

Your Vaillant boiler may make a kettling noise when the internal components get clogged due to limescale accumulation. It is very likely to experience this problem if you live in a hard water area. When there is limescale buildup, the water is heated too quickly, causing steam which makes a kettling sound. In such cases, the device may show up an F20 error code.

You will need a specialist to get your Vaillant boiler checked. The engineer will determine whether the limescale can be cleaned or whether the affected components should be replaced with new ones.

Thermostat and boiler not communicating

In case the thermostat and boiler not communicating, make sure to first check if the current room temperature is below the thermostat temperature. If it is, then the problem might be because the thermostat is located too far away from the boiler. Another thing that could cause your boiler to not respond to the thermostat is an issue with the thermostat itself. If that is the case contact the thermostat manufacturer and ask their representative to help you with the problem.

Pilot light not staying on

In most cases, a pilot light that doesn’t come on is caused by debris blocking the pilot light jet. It is also possible that the problem is related to an issue with the gas supply. Your boiler will likely need to be taken apart to be fixed in both cases, so you will need a qualified specialist to help you.

Boiler lockout

Vaillant boiler can lock out as a safety precaution. There are various reasons for this to happen including fan faults, too high pressure, a faulty gas valve, a problem with the ignition, blockage of the system and others.

Whenever your boiler is not firing or is locked out, you should seek help from a Gas Safe Engineer. Only a specialist can safely determine the source of the issue and recommend the most appropriate solution.

The Most Common Vaillant Boiler Fault Codes

In this section, we will provide you with a list of common Vaillant boiler error codes. We’ll delve deeper into the possible causes of these faults and how to fix them.

F 75 Vaillant Boiler Problem

F75 is a common boiler problem which normally occurs when the boiler is unable to detect enough pressure from the pump. The device will display F75 and it will not work until the issue has been fixed.

What are the possible causes of the F75 fault?

There are usually three possible reasons why your Vaillant boiler is displaying an F75 error code. The first and usually most common is a lack of boiler pressure. This could be due to a failure of the internal pump, which is more likely with older Vaillant boiler models. When the boiler’s pump fails, the circulating water is unable to move as quickly as it should around the heating system and to the hot water taps.

The second reason to blame for that F75 fault code is a blockage in the water pressure center or the pump. When dirt and sludge accumulate, they can clog the pump, causing it to spill incorrectly and eventually fail.

In some cases, the problem can be caused due to a faulty pump or pressure sensor.

How do you fix the Vaillant F75 problem?

The best thing to do if you see an F75 error code on your boiler is to seek help from a Gas Safe Engineer. The technicians will check the boiler and determine where the issue comes from, whether it is from the pump or the pressure sensor. They will also choose the most appropriate way to fix it. This may include flushing the system to remove all sludge and debris, replacing the pump or upgrading the faulty pressure sensor.

F22 Vaillant Boiler Problem

Another common problem with Vaillant boilers is F22, which indicates low water pressure. When the pressure falls below 1 bar, it is considered to be under pressure. It is an issue that almost all boilers face at some point during their working life. In terms of Vaillant models the low water pressure is a common fault in Vaillant Ecotec Plus as well as Vaillant Ecotec Pro 28.

What are the possible causes of the F22 fault?

If there is a sudden drop in the pressure then the issue is probably related to a reduced amount of water in the system, or in other words, a water leak. It could be due to leaks in the boiler, pipework, or radiators. Water leaks are usually easy to identify because they often cause damping of the floors or walls.

Another thing that may lead to a low water pressure problem is a build-up of air in the radiators. It can cause blockage and lack of water flow.

In rare cases, the F22 error code might be related to a faulty pump or pressure relief valve.

How do you fix the Vaillant F22 problem?

You may be able to solve the Vaillant F22 problem on your own in some cases. The first step is to thoroughly inspect the area for leaks. If nothing is found, try repressurizing the system using the boiler’s external or internal filling loop. If this does not resolve the issue and your boiler still displays the F22 error, you will need to contact a gas boiler and heating engineer. You will also need to seek professional assistance if there are leaks.

F28 Vaillant Boiler Problem

An F28 error on a Vaillant boiler usually means that there is an ignition failure. This can be a very unpleasant problem, especially if it occurs during the winter. The failure of the ignition will leave you without central heating and hot water, so it is definitely not something to ignore.

What are the possible causes of the F28 fault?

There are a few things that could prevent your boiler from firing up and heating your property. The first one that might be behind the issue is an insufficient supply of gas. The ignition process cannot be fed without fuel.

A faulty electrode or ignition lead is the next reason your boiler may display the F28 error code. If these components fail, the boiler ignition will be unable to generate a spark and activate the system.

Another thing that may lead to the F28 problem is a faulty gas valve. The primary function of the gas valves is to control the gas supply to the boiler. As a result, if they are damaged, it will be impossible to ignite the fuel and heat the water.

How do you fix the Vaillant F28 problem?

An insufficient gas supply, a faulty electrode or ignition lead, or a faulty gas valve are issues that must be diagnosed and repaired by a fully qualified engineer. This is not something you should attempt on your own.

The technician may need to remove the case of the boiler in order to determine the source of the problem and the best way to resolve it. In some cases, boiler ignition failure cannot be repaired, and you will need to replace your boiler.

F33 Vaillant Boiler Problem

F33 is another common error code which normally indicates that the pressure force measuring device or the air pressure switch does not turn on. The air pressure is a safety device and its role is to ensure the fan exhausts waste gases through the flue before starting the boiler.

What are the possible causes of the F33 fault?

An F33 error code has several possible causes. It might be due to a problem with the air pressure switch, fan or fan supply or flue. Many times this fault code appears due to a fan issue.

The fan has the important function of creating a draft and allowing the release of harmful gases from the boiler. In order for your boiler to start, the switch must first detect that the fan is running. This means that if there is a problem with the fan, your boiler will simply not ignite.

How do you fix the Vaillant F33 problem?

This is not something that you should attempt to fix yourself. It is recommended that you call a Gas Safe Registered Engineer. The specialists will check where the problem comes from and fix it. In some cases, the fan might need to be upgraded.

F62 Vaillant Boiler Problem

An F62 Vaillant error code usually means that there is an issue with the gas valve. This is a very important component in the central heating system because it controls hot water taps. When you turn on your boiler, the gas valve opens to allow enough gas to pass through for the ignition.

What are the possible causes of the F62 fault?

Some of the most common reasons for the F62 issue is a stuck or seized gas valve. In some cases, this code can appear due to an issue with the wiring or connection of the valve. Rarely your boiler may show up F62 error due to failure of the printed circuit board (PCB), or the boiler itself.

How do you fix the Vaillant F62 problem?

The faulty gas valve problem must be always addressed and fixed by a specialist who is qualified to work on gas appliances. Trying to deal with this job on your own might be dangerous because there is gas involved in this fault. The Gas Safe boiler engineers will be able to safely inspect the boiler as well as fix or replace the faulty component. In some cases, they may recommend upgrading the boiler and system.

F27 Vaillant Boiler Problem

The F27 problem arises if an incorrect flame has been detected. In other words, your boiler will display the F27 error code when the balance between gas and flame has been disrupted. It will cause a boiler lockout, resulting in no heating or hot water. The incorrect flame detection problem often arises with the Vaillant Ecotec boiler and Vaillant Ecotec Plus.

Sometimes the F27 error code may be related to an issue with the condensate pipe.

What are the possible causes of the F27 fault?

One of the most common causes of the F27 fault code is a build-up of moisture on electrical parts which in turn might be due to a leak in the heating system. Worn-out ignition leads may also lead to incorrect flame detection. Another possible reason for this boiler issue is a failure of the printed circuit board (PCB).

How to fix Vaillant F27 problem?

You should not attempt to repair the F27 fault or incorrect flame detection on your own because it could be dangerous. If you are experiencing such a boiler problem, seek assistance from a qualified gas boiler and heating specialist. Fixing the F27 problem frequently requires replacing the PCB. In some cases, you may need to get a new boiler.

Vaillant boiler not working no fault code

Vaillant boiler error codes are very useful in determining the root cause of the problem. But what if your boiler stops working but no error code is displayed? It’s a bit of a mystery that might require some guesswork to figure out.

There are might be various reasons behind this problem including frozen pipes, a valve fault, a recent power cut within your property and so on.

In some cases, you might be able to resolve the issue on your own. Here are some things that you may try.

  • check the energy supply if it is functional with a full connection;
  • reset your boiler – in some cases, the reset may resolve the problem;
  • examine your thermostat to ensure that it has not been knocked or set incorrectly;
  • return the settings to your preferences if your boiler has been reset to factory settings due to a recent power outage within the property.

If none of the above solutions has helped you resolve the problem and your boiler is still not working, contact a Gas Safe Engineer.

Frequently asked questions

Why does my Vaillant boiler keep firing up when heating is off?

This may happen if the comfort feature is being active. In such cases, your boiler will display a C symbol on the screen. In order to resolve it, you can simply turn the hot water control to 0 and then back to your desired temperature.

Can I reset my boiler myself?

You can reset your boiler by pressing and holding the reset button for a few seconds. If you completed the reset successfully, your boiler should fire up in a couple of minutes. In case of problems, contact a qualified engineer to inspect the boiler.

Should I turn my boiler off if it has a fault?

If your boiler displays an error code it is best to turn it on and contact a qualified boiler engineer. There are many possible reasons why your device has an issue including low water pressure in the system, failed ignition, incorrect flame detection and so on. Although some faults are not necessarily dangerous and are simple to repair, you should not attempt to do so on your own. Vaillant boiler problems need to be checked and fixed by Gas Safe Engineers.

If you’re experiencing issues with your Vaillant boiler, don’t hesitate to give our expert team a call today. We specialize in diagnosing and repairing a wide range of common Vaillant boiler problems, and our Gas Safe registered engineers have the experience and expertise needed to get your boiler back up and running in no time. Whether you’re dealing with a water leak, low boiler pressure, or a faulty thermostat, we’re here to help. Contact Gas Boiler & Heating Repair LTD now to schedule a service call and get your Vaillant boiler back in top condition.

If you have a Worcester boiler instead, you can read our post on the most common Worcester boiler problems and how to fix them. And if you’d like how to avoid costly repairs, check out our article on the boiler warning signs you shouldn’t ignore.