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Worcester Bosch Boiler Faults: Top 10 (and how to fix them)

Experiencing problems with your Worcester Bosch boiler?

As good as Worcester's are, and no matter how well you mollycoddle them, sometimes they can go wrong. It's a fact of life.

If you have an issue with your Worcester Bosch boiler, the good news is that in many cases, they can be resolved without the help of a professional - hooray!

In this guide, we explore some of the most common Worcester Bosch boiler faults, here goes...


Common Worcester Bosch Boiler Faults 

Worcester Bosch Boiler Problems

Worcester Bosch fault/error codes begin with the letters EA and will be displayed on the boiler’s digital interface. 

The purpose of these codes is to make it easier to identify the cause of the fault. 

Worcester Bosch Fault Error Code

You can see what the code means by looking it up in your Worcester Bosch boiler user manual. 


#1 - Worcester Bosch Boiler Losing Pressure  

Worcester Losing Pressure

Low boiler pressure is a relatively common issue that happens in most boilers at some point (even Worcester Bosch). 

Over time, it is quite normal for boiler’s to gradually lose pressure and need topping up.

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However, if your boiler’s pressure continually keeps dropping and is low, it is likely caused by a leak somewhere in the system. 

Worcester Bosch Boiler Pressure ProblemYou can identify low boiler pressure by checking the pressure gauge of your boiler. Typically, this is below the boilers main body and if it is low, the needle will be below the green region.  

The Fix 

If the low pressure is caused by a leak, then this is commonly the result of holes around the bends of pipes, where you may discover failed joints and seals.

Bosch Boiler Leak

Leaks caused by holes within major boiler components can also result in a loss of pressure, typically as a result of corrosion. 

If you spot what appears to be a leak, you should not attempt to open the boiler yourself and instead consult a Gas Safe Engineer.

If you find a leak inside your boiler, whatever you do, don't eat it

If there are no obvious leaks and this is the first time it has occurred, you may want to try topping up your boilers pressure yourself and then restarting your boiler. 

Read our full in-depth guide on low boiler pressure

#2 - Blocked Condensate Pipe (EA229)

Worcester Bosch Blocked Condensate

The condensate pipe is present in all modern boilers (all which are condensing boilers). Its role is to transport acidic waste from your boiler to your drains. 

When the condensate pipe becomes blocked in a Worcester Bosch the boiler will lockout and display the EA229 fault code. 

Worcester Bosch Frozen CondesateCondensate pipes usually become blocked when they freeze during the winter months. It commonly occurs when the pipe has been installed on the exterior of the home, where it is exposed to sub-zero temperatures. 

The Fix 

If your condensate pipe is blocked due to freezing, you will want to thaw the pipe out (pour warm water over the end of it).

Luckily, this is quite easy to do, but if you do not feel comfortable doing so, a Gas Safe Engineer will be more than happy to do it for you. 

Once thawed out, you will want to prevent it from happening again, which you can do by re-locating the pipe to a warmer location, so that it is no longer exposed to freezing temperatures. Ideally, so that the pipe spans the internal space of the home as much as possible. Again, a Gas Engineer can do this for you. 

Learn all about combi boilers in our what is a combi boiler guide. 

#3 - Boiler Leaking Water (EA338)

If your Worcester Bosch boiler is leaking, it will usually lockout out and display the error code EA338 or sometimes A281. 

Worcester Leaking Water

A leaking boiler can be caused by a few different things. The most common cause of leaking is superficial holes within the pipework, as well as broken seals, or valves. Sometimes, this can be caused by the pressure being too high.

Although, it is important to be aware that this can also be caused by more severe issues, such as corrosion to major internal components, such as the heat exchanger

The Fix 

A leak can be difficult to diagnose and even more difficult to repair, so it is recommended that you consult the assistance of a registered Gas Safe Engineer. 

If the leak is minor, then this may be able to be rectified using relatively cheap sealant.

However, if it is caused by corrosion to major components (such as the heat exchanger, or diverter valve), you should be prepared to pay for significant repair costs and potentially new replacement parts. 

#4 - No Power to Worcester Boiler 

No power to Worcester Bosch boiler

If your boiler is losing all power, then the issue is likely to be related to the electronics. 

For example, if your boilers Printed Circuit Board (PCB) is faulty it can result in a loss of power. The PCB is the major control centre of the boiler, so is essential for its function and controls key safety mechanisms. 

It can also be caused by a RCD unit that is tripped, or essentially any other electrical issue within your home. 

The Fix 

Typically, this will be related to the PCB (circuit board) which may be broken and need replacing or repairing.

Unfortunately, this is not cheap and will typically set you back a few hundred pounds for parts alone. Read our full guide on boiler PCB faults.

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Ultimately, if your boiler has lost power and won’t turn on it can be caused by a variety of different problems. The only way to find out the root of the problem is to have a registered Gas Safe Engineer take a look. 

Worcester PCB

Unfortunately, if it is the PCB that needs replacing and your boiler is no longer under warranty it probably makes more financial sense to get a brand new boiler installed rather than a replacement PCB. 

An old boiler no longer under warranty is likely to experience more issues and require more expensive repairs, so why invest in such an expensive component in a boiler likely to be on its way out?

#5 - No Hot Water to Worcester Bosch Boiler

No Hot Water To Worcester Bosch Boiler

If your Worcester Bosch boiler is failing to provide you with hot water, then there are few potential causes.

However, one of the most common causes of no hot water from the boiler is a faulty diverter valve. 

Faulty Worcester Bosch Diverter Valve

The diverter valves function is to control the flow of hot water, diverting it to your water outlets and your central heating. 

With time, the diverter valve can become worn and begin “sticking”, resulting in the valve only partially opening so that the water flow is negatively affected. The result is cold or lukewarm water. 

The Fix 

If your Worcester Bosch boiler has no hot water, it is not always the result of a faulty diverter valve, it could be caused by a variety of other internal boiler components going haywire.

As a result, it is essential that you get your boiler looked at by a registered Gas Safe Engineer. 

#6 - Noisy Boiler/Boiler Kettling 

Have you noticed your Worcester Bosch boiler suddenly making strange noises? It may be a sign of a problem. 

Boiler Kettling Sound

Commonly, a noisy boiler is caused by either limescale build-up on the heat exchanger, or sometimes an airlock in the central heating pump. 

When limescale builds up on the heat exchanger, it can overheat, resulting in the production of steam and bubbling, causing a whistling sound referred to as kettling. 

The Fix 

When your boiler is being serviced, the engineer can give your system a deep clean with high pressure and special chemicals designed to deal with limescale.

They can also add a limescale inhibitor to your system to help reduce the build-up of limescale deposits. 

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Unfortunately, if the limescale deposits have been left to fester for too long, the excessive heat can cause cracks and damage to components including the heat exchanger. These can be expensive to repair and replace.

Read our full in-depth guide on boiler kettling and our full guide on faulty heat exchanger problems. 

#7 - Pilot Light Keeps Going Out

Older boiler models don’t have an electric ignition like modern models and a result need to be remain turned on to ignite the gas within the combustion chamber.

Pilot light Going Out

In the event that the ignition is continually switching off, there may be an underlying issue with the boiler. 

Ignition that has issues like this may be a result of a faulty thermocouple turning the gas supply off, or a draught that is blowing the ignition out.

Carbon deposits on the pilot light are another potential cause, which may need to be cleaned to prevent it continuing. 

The Fix 

Unfortunately, since this component is inherently connected to the gas supply, it’s always recommended that you get help from a registered Gas Safe Engineer, who will be able to diagnose and resolve the issue safely.

Absolutely do not remove the case on your own boiler. It's super dangerous.

#8 - Boiler Not Responding to Thermostat 

Worcester Bosch Boiler Not Responding To Thermostat

Thermostatic control is how the majority of people control the temperature and schedule of their heating, so when your boiler stops responding to the thermostat it can cause haywire to your comfort and routine. 

The Fix

What are common causes of thermostatic syncing issues? 

To begin, try obvious things, like making sure the batteries aren’t flat (if it has batteries that is) and make sure it synced up with the current date and clocks if they recently changed. 

If the boiler still shows no sign of response, the next best step is to seek the assistance of the thermostat’s manufacturer. 

Curious to know which boiler brand performed worst? Find out in our report of the worst boilers

#9 - Worcester Bosch Boiler Overheating

Is your Worcester Bosch boiler showing an error code that related to overheating? 

Worcester Bosch Boiler Overheating

If your boiler is overheating it can be caused by a wide variety of underlying boiler problems including faulty central heating pumps, condensate pipe blockages or a blocked PRV. 

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Codes related to a Worcester Bosch boiler overheating include E5218, E5332, E9219 and E9224

The Fix

Overheating can be related to a variety of component faults, so the only way to be sure is to get it investigated by a profession Gas Safe Engineer. 

#10 - Boiler Locking Out or Turning Off 

Worcester Bosch Boiler Locking Out

If your Worcester Bosch Boiler is repeatedly “locking out” with no obvious explanation or fault code being presented, then it could be the result of a variety of problems, such as a faulty heat exchanger, faulty thermostat, or a faulty PCB

The Fix

If your Worcester Bosch boiler is repeatedly locking out or turning off with no obvious cause or error codes being presented, then the only sure way to find out what’s causing the issue is to seek expert assistance.

A registered Gas Safe Engineer will be able to diagnose and resolve the issue for you.  

Worcester Bosch busted? Get a free boiler quote today 

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