Keston Combi C45 boiler low flow rate

Hello Folks,

I have a Keston Combi C45 boiler, which is about four years old, & it is always serviced annually. Well, currently I am here to share my problem basically; the flow rate of the hot water is terrible. I am not sure what is wrong with the boiler. Is this merely a fault with boiler’s DHW blocking due to limescale with the passage of time? Alternatively, could it be anything else. Please help



Hi Joe, you are facing this issue due to the following reasons:

  • Jammed filter
  • Restricted pipework
  • Spearing jumper in the stop
  • Mains stopcock
  • Bad mains pressure

You can try the following ways out:

  • Clean the jammed filter
  • For restricted pipework, you can use a pipework with larger diameter
  • Replace the valve
  • For the mains stopcock, try operating or replacing the stopcock
  • Lastly, if you notice poor or reduced mains pressure then, do examine that each arrow on the stopcocks is going in the direction of water flow.

Keston Combi Boiler E03 error code

Hi Guys,

My five years-old Keston Combi boiler is showing an E03 error code since last night. I have restarted the boiler in order to fix the problem but no progress. Moreover, I am unable to get a gas supply from a Keston combi boiler’s burner as well. Please share your worthy suggestions.

Thanks in advance


Hi Rick,

According to the Keston Combi boiler’s user, guide an E03 error code means “faulty gas valve”. This valve controls the gas flow, which is being required by the burner & pilot light. At times, the valve becomes faulty & as a result, it does not work properly. Some other reasons behind the faulty gas valve are as follows:

  1. Defective unit
  2. Faulty connections
  3. Faulty printed circuit board
  4. Stuck valve

It is recommended to call a boiler engineer for adjusting or either replacing the faulty gas valve.

Keston Combi C50 boiler error code F3

Hello Everyone,

My three years old Keston Combi C50 boiler is displaying a F3 error code from last five days. I have tried to figure out the reason behind it but not succeeded. Thus, I am here to get some help from the experts.

Anxiously waiting for your valuable suggestions


Hi Mike, according to the Keston combi boiler’s user manual an error code F3 deals with the fault in the fan. You have to restart the boiler. You can do it by following the boiler’s resetting guidelines. If your problem persists, do call an experienced Keston combi boiler engineer in order to handle the problem in a professional way.

Keston Combi C40 boiler’s sudden explosive ignition

Hi Folks,

My Keston Combi C40 boiler, which is nearly six years old, is facing an issue of a sudden explosive ignition. It is quite dangerous. I do not know what happened with the boiler therefore, someone please share his/her views who has shared this problem.



Hi Josh, before coming to the main point, it is important to note that the problem of a sudden explosive ignition should be fixed instantly. Well, you are facing this issue due to the following reasons:

  1. The boiler’s slow ignition switch is out of order
  2. Compressed pilot flame

You can fix the problem by focusing on the following ways out

  1. If you suspect the slow ignition switch is damaged, try to replace it
  2. In case of a compressed pilot flame, try cleaning or replacing the boiler’s pilot widget assembly

Keston Combi C36 boiler error code L6


I have purchased a Keston Combi C36 boiler three years ago. I have not confronted any mentionable issue but now I want to seek help from experts as the boiler is not responding and displaying a L6 error code since last two days. Please guide me

Thanks for your suggestions


Hi Robert, L6 error code means, “False flame lockout”. You should try resetting the boiler by following the resetting instructions. In case, it does not work for you, do contact a Keston Boiler service center if the boiler is under warranty. Conversely, if the boiler is not under warranty you call a skilled boiler engineer for immediate help. I hope that this information will help you. Feel free to contact us for further help

Keston Combi C55 boiler lockingout over and over again

Hi Guys,

My two years old Keston Combi C55 boiler lockouts repeatedly. I am unable to understand the reason behind it. Due to this, the boiler is not working properly. Someone please tell me the ways of rectifying this problem?



Hi Rafael,

Your boiler is not having a required amount of pressure. When you set the pressure settings of your boiler quite low as compare to the recommended pressure then, the boiler cannot work in a way, as it should be. For this, you have to increase the pressure with the help of the filling loop. Afterwards, reset your Keston combi boiler. Lastly, do check for the drips in the below-mentioned parts of your boiler:

  1. Towel bars
  2. Expansion vessel
  3. Radiators
  4. Pipework
  5. Radiator controller

Keston Combi C50 boiler discharging cold

Hello Everybody,

I have a three years old Keston Combi C50 boiler, which is discharging cold water from last night. In order to fix the problem, I have restarted the boiler but no progress. My boiler is under warranty so, should I call a Keston boiler service center? Please help

Thank you so much


Hi Julian, it is a quite common problem in the Keston boilers. Keeping your problem in mind, I am going to share the some possible reasons along with the solutions below:

  1. Loss of the expansion vessel, you can fix it when the hot tap is open. Just verify & recharge the vessel
  2. Defective or blocked, for this expand the valve for relieving the value mechanism in order to replace or clear
  3. Defective pressure, for this you have to exchange the pressure & reducing valve
  4. Cross flow directly from the cold supply. To fix this check the mixer taps & fit.

Keston Combi Boiler out of order thermostat

Hi Folks,

I have bought and installed a Keston Combi boiler four years ago. I have not faced any mentionable issue up until now. However, last night as I turned on the boiler to take the shower, the water that came out was extremely hot. I am unable to understand the actual reason behind it. Besides, at times the Keston combi boiler fails to work properly. Has someone got any idea what is wrong with the boiler?

Looking for your valuable suggestions


Hi Tony,

An aging and out of order thermostat at times becomes non-functional or incorrect. Because of this reason, it will leads towards very hot water and occasionally absence of the Keston Combi boiler’s daily operation but it solely depends upon how the thermostat is acting out. Before fixing this issue, it is important to check that the boiler’s thermostat is working either properly or not. If a clock & mechanical, timer is set accurately and Keston boiler’s thermostat is motorized then, I would advise replacing it immediately.

Keston Combi C45 boiler central heating pump is noisy

Hello Everyone,

I have bought a Keston Combi C45 boiler one year ago. Someone please help regarding a problem which my boiler is having now a days. The signs are loud & weird banging sounds as I connect the boiler to the main power. The Keston boiler bangs like after 2-3 seconds. What is the reason behind it? Should I contact a service center?



Hi Jess,

After considering the above-given information, I am going to the share the few possible whys and wherefores behind ‘why your boiler’s central heating pump is noisy’? These reasons are as follows:

  1. speed settings are not correct
  2. internal parts of the Keston boiler are seized
  3. The central heating up is jammed due to sludge buildup
  4. Air locked

For detailed investigation, it is advised to call a boiler engineer.

Keston Combi C36 boiler not firing up

Hi All,

I have installed a Keston Combi C36 boiler three years ago. It worked well but now the boiler is not firing up. I am facing this problem from last few days. I have restarted it several times but there is no noticeable difference. What should I do? Someone please guide me

Thanks In Advance


Hi James,

If your Keston Combi C36 boiler is not firing up properly then, surely the fan is faulty. You will see an E05 error code on your Keston C36 boiler. Unluckily, this is not a matter of a DIY fix. Moreover, do not try to fix the problem at home. For this, you have to contact a skilled Keston boiler engineer, as he will be in better position to diagnose an issue with the boiler’s fan. In case, fan needs replacement, go for it to prevent further loss.