Keston Combi C50 Boiler No Power

Hi All,

My six years old Keston Combi C50 Boiler is not starting up; I tried a lot but all in vain. The timer is also not working. Can somebody please help me in identifying the exact reason behind it?



Hi Tom, if your boiler is not starting then do not forget to consider the following things:

Tripped RCD:

Do check the boiler’s RCD because if RCD has tripped than boiler cannot get the power, which is required for firing up.

Failure of PCB:

PCB is considered an important part of the boiler because it interconnects with some important parts of your boiler in order to run the boiler. In case of PCD failure, the boiler will not fire up.

Blown Fuse:

When there is a lot of power, a fuse will blow. As a result, the boiler will not get the power. It is a common fact that power cannot turn on without the running fuse. It is suggested to change it for getting the required power.

Keston Combi Boiler Sludge Buildup


My Keston combi boiler is making some strange noises. The pump is also struggling hard with the backpressure & is overheating constantly. Apart from this, the water flow on my Keston combi boiler is boiling quite hot but on returns, I am getting too much cold water. Is it something serious? Should I replace the boiler because it is five years old?

Thanks for the suggestions


Hi Michele

I guess there is sludge buildup in the central heating system. Sludge is just a dirty water. Different particles of the dirt/dust, which are present in the water, combine with iron oxide. As a result, this corrosion comes from the pipes, soldered joints, and radiators. In older boilers, this problem is very common. When this gooey liquid passes though the boiler’s central heating system, it deposits few of these particles. I would suggest you fit the scale reducers & magnetic sludge filter in your boiler to resolve this issue

Keston Combi C36 Boiler Lots of Hot Water but, No Heating

Hi Everybody,

I have bought a Keston Combi C36 boiler two years ago. It is a great boiler in terms of performance. Well, I am here to share a problem, which my boiler is facing nowadays. Whenever I turn on the tap, I get the hot water but there is no heating. What is the matter?



Hi Nick, this is the common symptom of the boiler’s faulty diverter valve. It is important to share that diverter valve on the Keston boilers work like a seal. It opens & closes in order to let heat up the hot water & water in a heating system, which gives heat to the towel rails and radiators. In case there is a lot of hot water but no central heating, you need to check the diverter valve as sometimes it trapped on the hot water side. Even though hot water is always a priority, the diverter valve cannot open to let the heating to easily warm up.


Keston Combi C40 Boiler Whistling Sounds

Hello Everyone,

I have a Keston Combi C40 boiler, which is about four years old. From last three or four hours, I am noticing some strange whistling sounds coming from the boiler. These sounds last only for few seconds. What is the matter?



Hi Tina,

Usually, the air trapped in the boiler is a major reason behind the whistling sounds. Even though, kittling and low pressure can also cause it. A faulty pump will produce various strange and weird sounds as well. You can fix it easily by bleeding the radiators or power flushing the pipes. This process will remove the excess air from the boiler. However, if whistling sounds are still there, you need to call a qualified engineer to check the pump & boiler as well.

Keston Combi C45 Boiler Switch off Automatically


My Keston combi C45 boiler turns off automatically after ten to fifteen minutes. I have restarted it but unluckily problem persists. The boiler is one year old & under warranty. Someone, please help me to sort it out immediately.



Hi David, generally there are three common reasons behind this problem such as:

  • Your Keston boiler is leaking
  • The pressure relief valve of the boiler is broken or damaged. If this is a case, you have to replace it immediately with the help of an expert Keston engineer
  • Lastly, another problematic thing is damaged thermostat as due to this, your Keston boiler will not be able to identify the water temperature. Conversely, the boiler will switch off automatically in order to keep the boiler away from overheating. I would advise you to check the flow of water.

Keston Combi C36 Boiler L2 Error Code


My Keston combi C36 boiler is giving a tough time from last two days as it shows the L2 error code. Restarting is also not working. I have tried every possible thing but no progress. Someone, please tell me what does L2 means & how I can fix it at home?

Thank you so much

Hello, here L2 means “Flame Loss”. It means that the boiler’s burner is not igniting or even failed to remain alight. Several different components of the boiler can cause it such as dirty/muddy spark electrode & ionization probe. Moreover, clogged condensate trap can also cause flame loss. If other appliances in your home are also not working then you have to check the gas supply. In case the problem persists, you can call an expert engineer to rectify it.

Keston Combi C40 Error Code F9

Hi Guys,

I have a Keston Combi C40 boiler, which is almost five years old. I am quite satisfied with its performance. I have not face any major problem up until now. However, from last few days, it is showing an F9 error code. I am unable to find the exact cause. Someone, please guide me.

Thanks in Advance


Hi Jake

F9 error code means “PCB Fault”. One of the most important part of any boiler is PCB as all the electronic components of the boiler communicate with the PCB. When PCB fails, all these components can malfunction. The best way is to call an engineer & run few important electrical tests by using a multimeter on the boiler. However, in the meantime you can look for the following things:

  • Leaks in the boiler
  • Fractures and cracks
  • Damaged or weal soldered joints

Keston Combi C55 Boiler Water is too much Hot


My two years Keston Combi C55 boiler is providing extremely hot water. I am unable to take shower. Does someone know the reason behind this issue? Should I call an engineer or replace the boiler?



Hi William, you do not have to replace your boiler. If water is coming out extremely hot, then it is likely to be the thermostat issue. If the central heating system is using a hot water cylinder or tank, then cylinder thermostat is a culprit. I am sure new thermostat will solve this heating issue. Nevertheless, if water is coming out too much hot from shower then, there is nothing wrong with the thermostat. The sealed units in the showers are susceptible to failing. If sealed units have failed while setting in the hotter set, it is likely that they are badly stuck there. Therefore, you have to replace the shower-sealed units.

Keston Combi C36 Boiler Some Radiators are Hot than Others


I am having a problem with my Keston Combi C36 boiler. From last three or four days, I am noticing that some of the radiators are working fine while others are not. In short, some radiators are hot while others are not. Can someone here please suggest a possible reason behind it?

Thanks a lot


Hi James, some radiators can be stubborn & do not heat as properly and evenly. The major effect is wasted energy, uneven heat and high-energy bills. I would suggest you check all the valves on the sides of radiators as these valves always control the flow thus, if one valve is locked or there is an uneven flow, you will get the uneven heat. The lockshield valve is the smallest valve & controls the water flow through a radiator. This valve may have to be opened widely in case the radiator is extremely far from your boiler. In other words, you have to adjust the valves in order to ensure that all the valves are getting sufficient hot water. However, if both valves on the boiler are opened correctly & heat is not releasing, you may have a backup issue.

Keston Combi C50 Boiler E44 Error Code

Hello Everyone,

I have bought a Keston Combi boiler three years ago. I have not faced any major problem with it but from last two days, it is showing an error code E44. I restarted the boiler but it does not help. I do not have any idea why my boiler is showing it again & again. Therefore, I am looking for some expert opinions.



Hi Kelly

According to Keston boiler’s user, manual E44 means, “Low-pressure water”. Sometimes, when the central heating system does not work properly, boiler always lost its pressure. You can check the current level of pressure by simply looking at its inbuilt pressure gauge. In case, the pressure is below 1 then, boiler might have a problem. Apart from this, you are advised to check for the visible leaks in your boiler. If you suspect any leaks, do call an expert boiler engineer for assistance.