7 Common Viesmann Boiler Problems and Repairs

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Last updated: October 31, 2023

Finding the right boilers for your home can be a daunting task. There are so many different brands and models to choose from, it can be difficult to decide which one is right for you. If you’re considering a Viessmann boiler, this guide will provide you with information about common problems and solutions.

If you are looking for a new boiler for your property or you need a boiler replacement and you want them to be durable, then Viessmann boilers might just do the trick. You can find these types of appliances in both oil-fired and gas-fired models as well as electric ones.

Viessmann boilers are a popular choice for homeowners because they offer high efficiency, long-lasting performance and improved energy savings. However, sometimes even the best quality boiler will have problems that need to be addressed.

In this blog post, we will discuss some of the most common problems that can occur with Viessmann boilers and provide solutions to help you get your boiler back up and running.

Getting To Know Viessmann Boilers

Viessmann is a well-known boiler producer for household boilers with a large selection of heating and hot water solutions to fit the majority of homes. Viessmann was founded in 1917 and produces high-quality German-engineered boilers that are innovative in design. The brand has even won several accolades for its boilers, including the Red Dot Award and German Design Award in 2015.

Viessmann combi boilers are renowned for their cutting-edge technology and come with a comprehensive guarantee to give you peace of mind. Each Viessmann combi boiler in the range is quiet, compact, and adaptable to room/environment temperatures. Viessmann combi boilers do not require a hot water tank or cylinder, as with other combi boilers.

In terms of pricing, Viessmann combi boilers vary significantly depending on your demands. The Vitodens 050-W range is often priced at around £860, while the Vitodens 111-W Storage combi boiler has an average price of £1,575. Vitodens 242-F series is the latest model available. These floor standing combi boilers with built-in solar technology cost around £6,087 and can save you over 50% on your heating expenses.

With this kind of quality, it’s no wonder Viessmann are so popular. However, even the best quality boiler will have problems that need to be addressed. In this blog post, we will discuss some of the most common problems that can occur with Viessmann boilers and provide solutions to help you get your boiler back up and running.

Viessmann Boiler Common Problems and How To Fix Them

Now that we have a general understanding of Viessmann boilers, let’s take a look at some of the most common problems and solutions. Though these types of boilers are well-engineered to provide years of use without trouble, there can be certain problems that occur with them. These issues range from small annoyances to potentially serious ones and should always be addressed as soon as possible.

If you have a Viessmann boiler, there is a chance that it may need some repairs or maintenance at some point in its lifetime. Some of the most common problems include:

Noisy Heating Pump, Or Cold Return Pipes

One of the most common problems with Viessmann boilers is a noisy heating pump or cold return pipes. If you have a noisy heating pump and cold return pipes, there’s a high chance your boiler will display an A8 fault code. This is frequently due to a dirty or clogged heating pump. Fortunately, both problems are quite simple to repair.

The circulation of water is monitored by the boiler. When the minimum flow rate has not been achieved, it will lockout, as is the case here.

Related Post: Is Your Boiler Making Noise?

How to Fix It

If you suspect that your heating pump is making noise, here’s how to fix it: The pump must be cleaned and checked for damage. The flow settings may need to be changed if the pump is in good condition, to provide the heating system with a boost of water circulation and meet the minimum flow rate requirements of the boiler. If there is no damage or blockage, and the flow rate of your heating pump has not been adjusted correctly, then you must adjust it.

There Is No Hot Water, But The Heating Is Operational

If your heating is still operable but there’s no hot water, there’s a chance that the elements of your boiler aren’t communicating. The Viessmann Vitodens 100 and Vitodens 200 are prone to this problem.

There are many causes for a diverter valve to stop working, but your boiler engineer will almost certainly identify a faulty diverter valve as the source. A boiler’s diverter valve switches between hot water and heating. If no diverter valve was installed, your radiators would get extremely hot whenever you call for hot water from the boiler. If your diverter valve is broken or jammed (on the heating side), it’s because the heating system works, but the hot water doesn’t.

How to Fix It

The solution to this problem is straightforward. Your broken diverter valve should be replaced as soon as possible because not only does it prevent hot water circulation within your heating system, but it also creates a risk of your radiators overheating.

A diverter valve might cost anywhere from £350 to £900 to replace (depending on the boiler type). Other parts in your boiler may be deteriorating as well, especially if it is more than ten years old. Have your engineer inspect the most expensive components in your boiler (including burner, heat exchanger, pump and fan).

The Burner Is Blocked

Without taking the boiler apart, it’ll be tough to identify a burner fault on your Viessmann boiler. And that’s something that requires the services of an expert engineer. The F1 error is the most frequent type of blocker for Viessmann burners. This will show up on your display panel. Some versions, on the other hand, will display A3, B0, F1, F-E1 and F-E2. This is generally caused by a faulty flue gas sensor.

How to Fix It

To fix this, you’ll need to check the flue sensor. The sensor is located on the burner and is responsible for reading the combustion process. If it’s dirty, you’ll need to clean it. But if it’s broken, you’ll need to replace it.

The best way to prevent your burner from becoming blocked is by regularly cleaning it. Make sure you do this every time you have your boiler serviced, and also once a year (or more, if you live in a dusty area).

Faulty Burner

A faulty burner is one of the most common problems with Viessmann boilers. F-B7, F-F4, F-F2, F-F7, and F-F8 are just a few of the fault codes found on the Viessmann Vitocrossal 200. The Vitodens 200 will display F10, F14, and F3. The boiler is blocked because there is no flame, no signal of a flame, or the flame is too weak.

How To Fix It

The solution to this problem is to have your engineer check if the flame sensor is working. It may just require a simple cleaning on other occasions.

A quick check of the burner and flame sensor, however, may indicate that they are working. The engineer will need to test the PCB if this appears to be the case. This connects with the sensor and burner. Neither of them will function if it’s damaged. If you’re thinking about high repair costs for a boiler with no warranty left, we’d probably suggest buying a new one.

The Boiler Won’t Fire Up

If you have a Viessmann boiler and it won’t fire up, there are few possibilities. According to Viessmann, this is a burner problem. If debris accumulates in the combustion chamber, it will cause the fault and an F5 error code will be shown.

How To Fix It

The quick fix for this is to clean and inspect your burner. The next step is to test the air pressure sensor. This switch indicates that the boiler’s operating range has been reached. It won’t ignite if there’s a problem with the sensor, wiring, or circuit board it talks to. It might be necessary to replace the sensor, repair the wiring, or replace the PCB as a result of this. Don’t just throw money away on an old boiler when you can get something new for less.  When the expenses climb beyond £500, it’s time to invest in a new boiler with a long guarantee.


Radiators Only Half Heating Up

Here are three examples to assist you in determining what is wrong with your Viessmann boiler:

  • Only Half of the Radiators Are Heating Up: This is the only sign that a boiler is faulty. It’s an indication of thermal control or water circulation difficulties.
  • It’s hot at the top, but it’s cold at the bottom: The underlying problem isn’t a boiler issue, but rather central heating sludge.
  • It’s cold at the top, but hot at the bottom: An airlock is indicated by radiators that are chilly at the top. To eliminate this airlock, bled the radiators. All you need is a radiator bleed key (like this one), and just open the valve until a faint dripping of water replaces the hissing sound of air.

How to Fix It

If you encounter any of these problems, assuming your radiators are just half heated (even temperature throughout), you’ll need to check for:

  • Heating pump problems
  • Temperature sensors for flow and return (NTC thermistors)

A professional engineer will be able to inspect the heating pump for leaks, a frozen motor, and whether it’s on the proper flow setting. They’ll then use a multimeter to check the electrical current and resistance of the NTC thermistors. If they’re broken, they must be replaced.

If the NTC thermistors are good, there might be limescale build-up around them. Limescale causes inconsistent temperature readings, so the NTC thermistors won’t work properly. As a result, their signals to the circuit board are intermittent. The limescale generally gathers close to the thermistor. The thermostat doesn’t signal the boiler to turn back on because it incorrectly thinks the overall water temperature is higher than it is. As a result, the boiler shuts off early.

Burner Lockout

This is a fairly serious problem because it won’t indicate what’s wrong. The F2 is the most frequent fault code. Although, older boilers (such as the Vitocrossal 200) might show problems including the E1, E7, E8, E9, EA, EB, EC and F2 error codes. Typically, there’s a blockage somewhere. The easiest place to begin is with your boiler’s central heating pump.

How To Fix It

How to fix this problem is to check the circulation. The burner will lock out if this circulation problem exists, but it is not typically the burner’s fault. The pump is required to move the heated water throughout the burner. If it does not do so, the boiler can overheat rapidly. An airlock in the pump is a typical cause of this problem.

You can try to clear the airlock by bleeding your central heating pump system. This is done with a radiator bleed key, and you just open the valve until a faint dripping of water replaces the hissing sound of air. If you’ve done everything correctly thus far, you’ll see a little trickle of water, which indicates that the pump has been fully bled of air. At this point, you may now close the screw.


If you’re experiencing any of the problems mentioned above, it’s important to have a professional take a look at your Viessmann boiler. Many of these issues can be fixed without having to replace the entire boiler, but it’s always best to consult with an expert. Keep in mind that not all boilers are created equal – and some are more prone to problems than others. So, if you’re in the market for a new boiler, be sure to choose one with a long guarantee.

For more information about common boiler faults for popular brands check out our guides for BaxiWorcester and Vaillant boilers.


1. Boiler FAQ – Viessmann