Viessmann F4 Fault Code Meaning & How To Fix Flame Detection Fault

James Elston
Written by James Elston
Updated on 22nd February 2024
Posted on 6th February 2024
viessmann f4 fault code

F4 Viessmann Fault Code Meaning and How to fix it

The Viessmann F4 error code indicates that your boiler does not have a flame signal or lack of flame, and hence cannot heat water for your taps, showers, or central heating.

Be aware, because this is most likely an internal issue or malfunction, you will require a Gas Safe qualified heating engineer to repair it.

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Customers rate Viessmann boilers as dependable, efficient, and long-lasting, which is useful for homeowners because Viessmann is such a well-known brand, and by going with a well-known name, you can be certain of receiving a quality product.

However, all boilers break down in time and if you are seeing the F4 fault code on your Viessmann boiler and it is over 10 years old then it may be time for a new one.

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A boiler service is one of the main ways to prevent a Viessmann f4 error code and other cases of a boiler breakdown:

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What does the Viessmann boiler F4 fault code mean?

If there is no flame signal, the boiler will not operate because the flame is utilised to heat water by burning the fuel that is introduced into the boiler.

When your boiler begins to heat up, it sends a signal to the PCB (Printed Circuit Board).

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When an F4 Viessmann error occurs, the PCB does not receive a signal indicating that the flame is properly commencing. When you ask for hot water or heat, your boiler sends a signal to all necessary components.

This includes the gas valve being opened and the burner lighting up. There is no flame detected in the burner in this case, suggesting that the temperature of the hot water and heating would not rise.

The boiler has been turned down as a cautious measure to prevent it from continuing to operate, potentially causing internal damage and gas leaks.

The boiler is likely to lock out in addition to the Viessmann Boiler F4 Fault code. This is done to keep you and your boiler safe. It typically ensures that the boiler is not harmful. In other cases, however, employing the lock-out prevents additional damage to boiler components.

Before fuel enters the boiler unit, it is burned by the boiler flame. As your boiler runs, it sends signals to your PCB, which acts as the boiler’s control centre.

Starting to see Viessmann error codes? Why not get a Viessmann boiler service to ensure that your boiler is running in the most efficient way possible?

What are the most common reasons for the Viessmann F4 fault code?

Flame Sensor – Faulty or Dirty

This is the component in charge of informing the PCB that a flame is igniting. As a sensitive electrical component, a buildup of carbon or other combustion byproducts on its surface may disrupt its performance; ensure that an engineer can safely remove and clean the item to avoid additional damage.

A breach in the porcelain insulation around the item might cause it to stop your boiler from firing up.

If the flame sensor generates the F4 fault, it is likely that the ignition mechanism is going properly but is not being recognised. If this is the case, you may have noticed that the boiler begins but then stops.

Problems with the boiler’s wiring or connections

Every electrical component in the gadget is linked to the PCB, allowing it to accurately identify when each stage of the heating process occurs.

These connections might become loose due to vibrations within the boiler or typical wear and tear over time.

If you’ve recently noticed loud vibration sounds, a larger component, such as the pump, might be malfunctioning.

Electrical components may fail as a result of a general fault or external damage. The most common source of this within boilers is moisture from internal leaks.

Because certain electrical components are so delicate, even a drop of water might cause damage.

Gas Valves that are Stuck

The flow of gas into the boiler is controlled by these valves. They remain closed until the boiler begins to heat, at which point they slide open to enable gas to circulate.

If a faulty gas valve is jammed in a tight position, the boiler will try to ignite but no flame will be lit owing to a shortage of fuel.

As a result, if you experience the same issue, the sensor will be unable to detect a flame and will transmit this to the PCB, displaying a fault code such as F4.

Malfunctioning valves might become trapped in a fully or partially closed position periodically or totally. This is especially common in older boilers since the valve is a mechanical component that may eventually break.

Burner Jet Blocked

Once the gas valve opens effectively, the jets are the parts which burns the gas that enters the boiler.

Because their holes are so small, even trace quantities of carbon and debris from the fuel-burning process might clog them.

This hinders the necessary quantity of gas from flowing freely into the boiler, making it faulty and reducing its ability to create a flame.

Faulty PCB

Because the PCB is in charge of interpreting all electrical signals, any fault in it might impair its ability to confirm certain operations, such as detecting the flame.

Loose connections, electrical failure, and water damage are all typical problems with the PCB and the boiler’s other electrical components.

If you have a faulty or damaged PCB, you may have observed additional problems with the boiler’s operation, such as it cycling on and off very rapidly.

Ignition Lead Faults

These pieces are in charge of igniting the gas after it enters the boiler. If it becomes a faulty ignition lead then it is unable to do so consistently, there will be no flame to detect by the sensor.

As electrical components, they might lose power on their own or encounter problems due to faulty wiring and connections, as described above.

Water from within is the most prevalent source of damage to these parts.

Our Expert Gas Safe Engineer Says:

All of these problems will cause the F4 error code and unfortunately if your Viessmann boiler isn't under warranty, then you will need to call an engineer to fix the issue

James Murfin

Gas Safe Registered Heating Engineer

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Who should I contact if I have an F4 fault code on my Viessmann boiler?

You should contact a Gas Safe registered engineer that is registered to work around the UK and should be able begin to work on repairing your boiler. If they see the Viessmann F4 fault the will search for anything that might interrupt your boiler by creating a flame, which will include inspecting the:

  • Ignition lead
  • Spark generator
  • Boiler Burner 
  • Flame detector
  • Faulty Gas valve
  • Faulty PCB
  • Faulty Electronics

Can I fix a Viessmann F4 fault code myself?

There are just a few boiler flaws that you can repair yourself, and this is certainly not among them. You should also avoid attempting to reset your Viessmann boiler.

The reset mechanism included in modern boilers is developed to be used after the problem has been rectified; it is not a repair procedure.

To fix the problem, your engineer will need to test numerous parts as well as disassemble your boiler. Only Gas Safe engineers are permitted to work on gas boilers. As a result, we recommend contacting them as soon as possible, to prevent further damage.

What electrical features do I look for?

The very first thing a boiler engineer wants to do is physically check your boiler’s internals. This can quickly disclose any water damage or general wiring and connection problems. In certain cases, slight damages can be restored.

Along with securing connections, wiring repairs may be sufficient to restart your boiler. And, the idea of a reset will eliminate the F4 fault code on your boiler.

A visual inspection does not always reveal possible issues. As a result, your boiler engineer may want to use a multi-meter (the resistance readings from electrical parts which can then be cross-referenced to the acceptable measurements for each component.) If some elements have fallen loose or stopped working, it may be able to reconnect or replace them without incurring major costs. While materials are inexpensive, labour costs vary depending on how long it takes to detect a fault and how difficult the repair is.

Is my burner to blame for my Viessmann F4 fault code?

A burner is indeed the part that enables you to not only start but also keep a flame going. Over time, this carbon can start to build up in the burner, which can then lead to small blockages. This is more likely to cause a change in the flame signal than it is to prevent the appearance of a flame.

When there isn’t a flame, your engineer should concentrate on the jet. These little jets deliver gas to the burner. Because they are so little, they can quickly become clogged. Even the slightest quantity of carbon particles in the jet can prevent a flame from forming.

The jet and burner are unlikely to need replacing. Rather, the boiler engineer knows the jet must be removed, cleaned, and reinstalled. If you’ve got a constant gas supply, the boiler may now be restarted to remove the F4 issue code on the boiler.

Problems with the ignition lead or spark generator?

The ignition’s lead and spark generator are essential pieces of your boiler’s ignition system. If they are defective, there will be no spark producing, will not be able to see any flames, and the F4 fault code will be showing.

Your boiler engineer will not only want to examine these parts for power, but also symptoms of moisture. Even a trace of water damage on the spark generator or ignition lead can cause both devices to fail.

What role does the flame sensor play when there’s no flame upon ignition?

Your boiler is equipped with a number of sensors. Some sensors measure water temperature, gas pressure, and air pressure, while others monitor the flame your boiler has.

When you turn on the heat, the boiler activates the fan, creating a draught that pushes gases down the flue. When this is operational, gas enters the burner through the jet and is ignited. The PCB is now expecting to detect a signal from the flame sensor indicating the existence of a flame.

If the flame sensor fails, the PCB will not be notified of the presence of a flame. Whether it is present or not, the boiler will lock out leaving you with no hot water and displaying the F4 error code.

As a result, the boiler engineer must ensure that the flame signal test is passed. They will need to replace the flame sensor if they discover that it is not receiving power or is receiving intermittent power.

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Can a faulty gas valve cause a flame detection fault?

As stated previously, the gas valve admits gas into the burner when heat is necessary, however, gas valves are mechanical components that might wear out over time. We commonly find jammed gas valves.

Because the gas valve is slightly open, gas is sometimes let into the burner when it should not be. This is known as “letting by.”

In the case of the F4 error code, the gas valve is most likely jammed closed while it should be open. That means it can’t supply gas to the burner via the jet. As a result, they cannot burn and a flame detection failure occurs.

The boiler engineer inspects the gas valve’s electronics and liberates it. If the valve isn’t in great condition, the boiler repair firm you choose will most likely recommend installing a replacement gas valve.

Does F4 mean heat exchanger and pump problems

A faulty heat exchanger or faulty heat pump are typical causes of springing leaks and can be costly to replace, necessitating services such as a power flush to remove limescale or sludge that caused the damage.

A leak in your heat exchange can also be spotted by persistent low boiler pressure and this must be fixed by a Gas Safe registered heating engineer or in worst case scenario replace your Viessmann boiler.

How much does it cost to replace a gas valve?

A gas valve replacement, on average costs, £275 and takes a day to install for a Viessmann boiler. The F4 error code should no longer be showing on the screen after replacing the valve and restarting the boiler.

Is the PCB to blame?

The PCB is basically the boilers brain telling your boiler what to do and when to do it, whilst ensuring that all parts are working correctly.

A few things will happen if the PCB fails. To begin, you will notice that your boiler functions on occasion. It can shut the boiler down which is very common, as a lockout protects you and your boiler from more damage but it may cause the boiler to start up when it isn’t required.

On the other hand, it may receive irregular or non-existent signals from boiler components which may mean that the rest of the boiler is perfectly fine, but your PCB is telling you and the boiler otherwise. As you can imagine this is a big issue.

In other cases, securing cables and connections is all that is required. In the worst-case situation, the PCB must be substituted.

How much is it going to cost to a PCB?

it is going to cost, on average £450 including components and work to replace the PCB on a Viessmann boiler.

Other Viessmann Troubleshooting Problems:

Some of the most common Viessmann Boiler Problems include:

When Is It Time To Replace Your Viessmann Boiler?

viessmann vitodens 050-w

The average boiler has a lifetime of 10-15 years. However, if you need to hire an engineer on a frequent basis, a new boiler may be a better option.

Other indicators that a replacement is required include noisy boilers or radiators, as well as leakage. Even the best combi boiler will fail one day.

Because older, less efficient boilers have higher energy costs, a replacement may not cost much extra during its lifetime.

Who Are Viessmann?

Viessmann is a family-owned and operated business that values quality. The founding of this company was in 1917. It has now evolved from a tiny heating system provider to an internationally recognised household boiler brand.

Viessmann logo - Viessmann f4 fault code

Viessmann boilers come in a variety of types, ranges and models – check out the:

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You must have your boiler serviced regularly.

We have you covered at Boiler Central, and you can compare standard boiler protection right through to full home cover options. With our complete cover, you can have peace of mind. We have the best boiler cover plans to guarantee that you not only get a great bargain but also a quality service that covers all you need to ensure minimal disturbance in your life if something goes wrong with your boiler, central heating, or home.

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Choose the best boiler service plan

We provide boiler cover which includes the cost of boiler servicing, so you can rely on us to assist and check your boiler on a regular basis instead of making a yearly appointment.

When your central heating system is satisfying and you just want to guarantee that you have a boiler service every year but do not want to pay a flat amount every 12 months, you may divide the cost into monthly boiler service plans.

You get the same amazing yearly boiler service to ensure your boiler is functioning efficiently and effectively, plus we remember and call you to book a boiler service every year so you don’t have to. Whether you want a service for your combi boiler, service for your system boiler, or service for your conventional boiler, we can meet your needs.

It may be time for a new Viessmann boiler.

If you searched Google for “buy a new boiler,” you are unsure of what boiler manufacturer or model you require, or if the cost of a new boiler is right for you.

Boiler Central allows you to select your installation date from our booking calendar as soon as the next day, and we handle everything online.

It has never been easier to acquire a boiler upgrade, and we are committed to making the process as simple as possible.

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Written by
James Elston
James Elston Director Of Boiler Central
Posted on: 6th February 2024

James Elston is our resident boiler replacement and heating expert here at Boiler Central. With over 20 years experience in the boiler installation industry, James ensures that he knows everything there is about our Gas Safe boiler installations, energy saving and home heating solutions. This can be from simply procuring the latest best combi boilers, to reviewing and ensuring that Boiler Central maintains the highest standards across our boiler installation company.

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