10th May, 2022

Boiler Not Working? Most Common Problems (And Fixes)

A complete guide to getting that boiler working again and some common fault codes and how to fix.

Boiler Not Working? Most Common Problems (And Fixes)

Important, Smell Gas? If you think you have a gas leak or can smell gas, leave the house and phone the National Gas Emergencies number immediately on 0800 111 999.

How to fix a boiler before calling an engineer

  1. Re pressurise your boiler

  2. Reset your boiler

  3. Bleed your radiators

  4. Change thermostat batteries

  5. Make sure you have credit

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Why is my boiler not working?

There are a lot of reasons why your boiler may not be working. Some Common fixes include a frozen condenser pipe, no gas to the boiler, pressure being too low, a leak on your existing system, faulty controller and more.

Boilers are complicated pieces of equipment, but many people rely on them to get hot water and a proper central heating system in their home.

Unfortunately, like all complex machines, they can sometimes simply break or stop working, even during the installation process.

Whether it is an issue with the radiators, the water supply or just a misplaced valve or just your boiler not working, it can be hard to notice your boiler issue until the problem has already started putting pressure on your other appliances.

Unlike a computer a new boiler is not quite as simple as turning it off and back on, however this can sometimes work.

Here are some of the top boiler problems which may avoid you having to buys a new boiler.

Top 5 broken boiler problems and how to fix them

Before having to cash out for a new boiler here are the top broken boiler issues that can plague most modern boilers and possible solutions. Some are minor, but others will require an engineer to be called out to repair it.

Knowing the difference between a DIY boiler repair job and a situation where calling for a full engineer quote is important.

Boiler not working common fixes for old combi

1. Leaking or dripping boiler

A leaking combi boiler is one of the most well-known causes of a boiler not working. A leak can spring up anywhere in the system and drop the boiler pressure significantly - if it's after the boiler pressure gauge, it might not even get picked up by the readings.

Check for signs of leaks on your system

Check everything that's exposed, such as radiators, as well as the boiler itself. If you don't see any obvious signs, then you might have to contact an engineer and get them to look at the entire central heating system and boiler themselves.

Does the boilers pressure keeps dropping?

If you find that the pressure on your boiler continues to drop after topping up this may be a sign that there is a leak on your existing system.

These type of leaks can be hard to find as it means following your pipework from the boiler throughout your home to every connected point.

We also have a more detailed guide on what to do when your boiler pressure keeps dropping

✅ How to fix a leaking or dripping boiler?

If this isn't due to the boiler pressure dropping which you cant fix through our guide above and you cant find any visible signs of leaking on your radiators or boiler then it's time to call an engineer out to investigate further.

2. No pilot light to the boiler

This can be quite noticeable too since it stops the boiler from actually heating up everything that passes through it. No pilot light or thermostat means that your boiler will produce no central heating or warm water.

Very few new boiler designs use an actual flame anymore, so you'll be relying on technology instead: if you can't restart it, get an engineer to take a look since they're more likely to identify the damaged components correctly.

✅ How to fix no pilot light?

If you are on pre-paid meter make sure you have credit. Contact the gas company to ensure you have a live supply. Restart the pilot light, see your boilers manual for more information on how to do this as it may vary for each boiler brand.

3. Gas problems

These aren't very common these days but can be extremely dangerous. You'll need a Gas Safe Registered engineer to handle these problems since they're certified and qualified to offer engineer services and/or a quote concerning boiler systems that use gas as fuel.

Even something as small as a broken valve can cause a gas leak or a build-up of flammable fuels, so don't attempt to fix it yourself unless you're also a Gas Safe Registered engineer.

✅ How to fix issues with no gas to my boiler?

Call the National Gas Emergencies number immediately on 0800 111 999

4. Controller / thermostat timer scheduled

If you find your boiler is not firing up for the central heating system at a scheduled time, there might be something wrong with the scheduling timer: this is mostly a feature of electronic boiler models that have built-in online connections or time settings.

It could be something as small as the clocks changing or the options being set incorrectly, but it can still be irritating to deal with. Try to adjust the settings or refer to the manual if you don't know-how.

✅ How to fix thermostat timer schedule?

See your thermostat manual on advice on how to setup correctly.

5. Fuel and electricity issues

This is always important since your boiler needs them for even its most basic functions. If you don't have any electricity or gas heating water up, then you need to try and reconnect everything.

This can be incredibly risky if you are untrained, but a professional quote can be higher than expected depending on the problem. We would advise not to do this yourself and call a Gas Safe engineer.

✅ How to fix boiler electricity issues?

If ever in doubt then please call an engineer, messing with your boiler may void the manufactures warranty.

Other Reasons for Your Boiler Not Working

Sometimes, you will notice your boiler not working regardless of what you try. This is most common with boilers that were recently installed or modified since there is always a chance that something went wrong in the installation.

If you are not facing one of the common problems, then it might seem like there is not much that you can do to fix the problem.

Identifying the issue can be important, and not just because you want to fix it: if you know what is wrong, you can keep yourself safe and make sure that the boiler does not break. But what should you be watching out for?

Complete Failure

It is possible that a boiler is just broken beyond your ability to repair it. This could be because something damaged an internal circuit or thanks to water, causing major rusting on some important components.

In situations like this, you might just have to consider the boiler a lost cause unless you know a way to solve the problem.

Keep an eye out for major signs of damage to specific parts of the boiler if you are able to. A boiler might stop working because a certain part of the system, like a specific pipe, had been completely destroyed due to normal wear and tear. If you can replace that part, you might be able to fix the issue fairly quickly.

✅ How to fix boiler not working?

It depends on the problem. If a single component is damaged to the point that the boiler does not work, try to replace it, or get a licensed engineer to repair it.

On the other hand, if multiple parts of the boiler are physically broken beyond a level that the average person can fix, you might just have to shut it off and get a replacement.

No Power

Most boilers need some form of power, especially modern ones that use electronic Smart technology. Without power, you usually do not have a boiler at all: only some of them will even heat water without electricity.

This means that losing electricity can lose your heating as well, and it won’t always be obvious that the system has no power.

This does not have to mean that you lose power to the entire house – if a power cable is damaged or a water leak breaks the outlet that the boiler is plugged into, then the problem might be less related to the boiler and more related to powering it in the first place.

Wet power cables can also indirectly damage circuits within the boiler, so check that the system has not been harmed to the point that it no longer takes in power correctly.

A leaking boiler is more likely to cause power problems than one without a leak, but neither is guaranteed.

✅ How to fix no power to my boiler?

Ensure that you can supply power to the boiler by replacing or fixing whatever is causing the problem. Check cables for cuts or water damage.

Turn outlets off and back on. See if there are other power problems in your home and consider using a generator or extension cord to provide an alternate source of power.

Flame and Pilot Light Issues

Many boilers rely on a pilot light to heat up water, so losing that flame loses the ability to heat the boiler’s water at all. For example, if there is no flame in the boiler (or the flame is irregular), then there might be more carbon dioxide than oxygen inside the boiler, meaning that there is no air for the pilot light to consume.

There is also the possibility that the flame is not lighting at all, especially if the components to create the original pilot light have worn out. Older gas boilers can run into a lot of small faults that might cut off the flow of gas or break the pilot light.

✅ How to fix pilot light issues on my boiler?

Check the supply of gas to the pilot light. Make sure that there is oxygen available. Call a specialist or Gas Safe engineer as soon as possible to avoid harming yourself or creating fires that you can’t control.


Corrosion is a common problem that a lot of boiler models struggle with, especially when they have been operating non-stop for multiple years at a time.

Like other types of damage, corrosion can either impact a single part, or the whole boiler, meaning that some cases are much more serious than others. Sometimes it can stick around and plague a boiler for years if you do not fix the cause quickly, too.

Dealing with corroded pipework and boiler components means that you will usually just have to replace them since you can't easily fix them by yourself.

This often means that you will either need to buy specific parts or find alternatives that you can take from another old boiler.

✅ How to fix corroded boiler pipes?

Replace corroded parts if possible. Replace the entire boiler if the damage is too widespread to fix with individual parts.

Get a specialist to check the cause of the corrosion if you are worried about it happening to your replacement parts.

Boiler Resets

It is possible that a power cut or other reset of the boiler will have changes your settings, which can mean that normal timer options and other automated features won’t be saved.

If you recently had power issues or your boiler was disconnected from your power system for maintenance, then you might have to set it up again and re-enable any settings that you want to use.

Some Smart boilers might also have to be re-paired with other devices that they were tied to, so make sure to check which devices the boiler is still connected to after a power cut. It is not always easy to tell what has changed without looking at the boiler's settings yourself.

✅ How to fix boiler after power cut?

Adjust the settings and schedules on the boiler after a power cut (or any other major changes) to make sure that they are still the same. If the boiler did not fire up automatically you can power off the boiler for a few minutes and try turning it on again, if this fails then please call an engineer.

Keep a note of what your settings are so that you can apply them again after a power cut. Make sure that Smart boilers are still paired properly and have not been disconnected from other devices.

Why would a boiler stop working?

The general purpose of most new boilers is to heat up and transport water to various different appliances. Almost everybody who owns one got their boiler for hot water, so you can usually assume that it is an issue with the supply or pipes in some way.

If even a single pipe or valve is broken, it could lead to the entire boiler system losing water pressure and struggling to keep the flow moving. On the other hand, if it is the central heating that breaks, the water might not be warming up properly at all.

Boiler problems with pilot light

Simply just stopped working?

In general, if your boiler simply "stops working", then there is something wrong with the system that's affecting its ability to actually provide the hot water you need.

A small leak or worn-out heating system can reduce its efficiency or make the boiler pressure drop slightly, but it wouldn't break everything in an instant, which hints at it being a bigger problem.

How do you restart a boiler?

Different types of boilers may require slightly different methods, however you generally need to do the following:
Press the reset button and hold it down for 10 seconds. Wait for approximately 2-3 minutes, as the boiler may be starting up. If the reset has been successful, then the flame will ignite within the boiler.

1. Resetting your boiler

To get it working again, you'll have to reset it, even if the problem has been fixed - with no reset, the boiler won't "know" that it's repaired.

This lockout or shutdown feature can activate for various reasons, a key one being unsafe conditions, such as the wrong type of gas or a sudden spike/dip in electricity.

2. Find the right reset button on your boiler

It's not too difficult to reset your boiler, but it can take a while to find the required buttons.

Almost all modern boiler models, both electric and gas appliances, have a restart button somewhere on their body, either in the main control panel or placed around the back like a last-ditch safety measure.

✅ How to reset your boiler?

Almost all modern boiler models, both electric and gas appliances, have a restart button somewhere on their body, either in the main control panel or placed around the back like a last-ditch safety measure. You'll have to get access to the system yourself, so be prepared to open up the cupboard or panel it's placed behind. Please always check the boilers manual before attempting this to find the reset switch.

3. Check the boiler manual for information

If you can't see a button, you should check your boiler manual or an online guide to help you track it down. Some models have them hidden away to stop users from accidentally resetting the system while they're adjusting different parts, but others will put them in very visible spots.

Be careful when following a boiler's manual instructions, since your boiler may be installed at an angle rather than straight ahead.

If you have a Viessmann 050-W combi boiler you can see the online manual here for more information.

4. Give it a little time..

Once you find it, you should follow the manual again for advice. If you can't find any information, try holding the button for around ten seconds: this is more than enough time for an average boiler to fully restart - then you just need to wait a few minutes for the system to re-ignite.

Avoid pressuring the button again unless you're absolutely sure it hasn't worked since this can break some of the important components inside.

Fixing a broken boiler

How do I know if my boiler is broken?

The easiest way to tell if a boiler has stopped working is to see if there's no hot water. A lack of central heating, radiators that don't provide heat or other obvious signs could hint that something is very wrong with the boiler in terms of its heating system - either the heating itself or the fuel/power that's needed.

If a boiler is still clearly showing that it's using power but still not working (this is most obvious on electrical ones, since they may have power gauges or digital displays), it's clear that the problem isn’t a lack of fuel. In these cases, simply restarting the boiler or re-connecting it to the electricity/gas mains won't be enough, since the issue is still in there somewhere.

The pilot light may be out

If you notice your gas boiler not working as it should be, you might have to look at the pilot light or the gas supply and figure out how much fuel is actually getting through.

All gas appliances need a near-constant gas supply to work correctly, and if none of it gets to the pilot light (or the pilot light isn't working), then it can't ignite and ensure that you get the temperature that you need.

These are only surface-level problems, though: there can be some much more serious issues that take a lot longer to fix. For example, if you notice that the boiler pressure gauge has dropped by a significant amount, then a pipe or valve has broken in a way that makes it hard for water to move around properly.

Frozen condensate pipe?

On the other hand, if it's too high, your condensate pipe might be broken or frozen instead, meaning that the water's not able to leave the system properly and is getting backed up.

Both of these can be dangerous if left unchecked, so you need to fix the pressure right away: for low boiler pressure, look for leaks in the pipes (both before and after the water passes through the boiler), and try to fix high-pressure problems by getting the condensate pipe or some key valves replaced.

✅ How to fix a frozen condensate pipe?

You can often fix this yourself. Boil your kettle and top up in a jug with cold water until the temperature it hot but not boiling. Pour this over the frozen condensate pipe outside to clear any frozen blockage. Repeat the process if needed.

Preventing your pipes from freezing

Time to get a qualified engineer out

It's not always easy to tell if your entire boiler is broken, but if it is not working and doesn't seem to be turning back on even if you reset it, then there is likely a major issue with the entire system.

At this point, getting an gas safe registered engineer involved or potentially getting a new boiler is key: every second of a boiler not working is a second of wasted fuel, as well as potentially increased damages and repair costs.

Always make sure your engineer is Gas Safe registered, you can check this on the Gas Safe register list https://www.gassaferegister.co.uk

Boiler Error Codes

Some boiler models have error codes to help you identify why they are not working. They can be a shorthand way of identifying many different boiler issues and might even give you some insight into how to fix the current problem.

Always be sure to check your boiler manual if you notice that it's started flashing or displaying digital codes since getting them wrong can be a massive problem in its own way. The boiler codes may vary slightly for new boilers.

Here are some of the most common: make sure you follow them as closely as possible if they apply to your boiler.

Viessmann Boiler Error Codes:

  • 5C/D/E/F = Communication fault with the boiler.

  • D4 = Faulty safety equipment or internal BUS.

  • 0C = No power/flame signal is still running, but boiler is turned off.

  • C1 = Lockout due to voltage fluctuations.

  • F5 = Problems with gas supply.

  • B4 = Major internal fault.

  • B5 = Caused by external safety equipment.

  • 0B = Wind damaging the vent system/water is flowing the wrong way.

  • FE4 = Undervoltage.

  • 0F = Maintenance needed.

  • A3/B0/F1/F-E1/F-E2 = Faulty programming (automatically switches back to factory default settings).

  • B1 = Internal electronics fault.

Alpha Boiler Error Codes:

  • 1 = Complete ignition failure.

  • 25 = Overheated.

  • 37 = Low voltage.

  • 24 = Boiler control panel jammed.

  • 44 = Safety lockout due to various issues.

  • 0E2 = Flame sensor not working.

  • 0E37 = Low boiler pressure.

  • No lights = Electrical fault.

  • Various combinations of flashing yellow and red lights = Severe fault.

Worcester Boiler Error Codes:

  • B7 = Replace boiler control board.

  • D1 = Boiler overheating and/or sensors are overheated.

  • E5 = Primary sensor has overheated.

  • A1 = Boiler contains no water.

  • C1 = Boiler fan has stopped.

  • 260 = Sensors are disconnected, and boiler contains no water.

Selecting the right gas safe engineer Gas Safe Registered Always check the Gas Safe register to make sure any engineer that has been asked to work on your home is qualified.

If you discover the engineer is not registered with Gas Safe then kindly ask them to leave your home, you can also report them to Gas Safe.

Communication Make sure the engineer understands your request. They can advise based on their experience but at the end of the day it it your home, and the job should be completed to your specification. Boiler Not Firing Up? If your boiler is not igniting, there are a few possibilities that it could be.

The valve could be blocked, seized, or damaged to various wired connections. If the pilot light is out, this usually means debris has blocked the jet and could be preventing the boiler from firing up.

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