Keston 40 error E03


I have a Keston Combi 40 model, which is 6 years old and it worked really fine till now. Last week it showed error E03. I restarted and  it helped… for a while. Today boiler switched itself off showing again E03 error message. What does it mean and how to fix it?



Hi Jim

Error 03 means that your gas valve is either not connected or faulty. Considering it was working for the last 5-6 years, I would say it is faulty and need to be replaced. You can replace yourself (if you have proper qualifications) or call Keston service. They will exchange it in less than an hour

Keston C55 no hot water

Hi Folks

My Keston C55 is only 2 years old stopped providing hot water. Today morning I had a cold shower for the third time, I have enough! Does anyone know what may be the problem. I add that there is no error message being displayed and it is proving the central heating.


Hi Alex,

Unfortunately if your boiler doesn’t display any error message it will be difficult to help. It can be thermostat, wrong setting of heat/hot water circuits. Did you try resetting? I would advice to call Keston service. Your boiler is still under warranty, you can always request a replacement appliance

Keston C40 ignition problem code E02


My Keston C40 boiler permanently fails to ignite. It shows E02 error. Has anyone an idea what does it mean? Will simple restarting help? Or I should call the service straightaway?



Hi George

There are several parts which failure can cause E02 error: blocked condensate,the gas valve, high voltage cable, ignition & flame detection electrode, PCB or soothed burner. In your position I would try restarting myself, in many cases it would help to solve the issue- at last temporarily. If problem persists call service- to many parts to replace if you don’t have proper qualifications.

Keston C55 leaks

Hi All

I have Keston boiler model 55 and was pretty happy with it for years now, unfortunately I realized last week that boiler starts to leak. What is wrong? Any idea how to fix it

Best Regards



Hi Robert

This is commonly know problem with C55 / C40 Keston boilers. To fix it you will need to replace heat exchanger gaskets and most probably fan. Repair doesn’t take much time, but should be done very fast after realizing the fault otherwise your boiler will break completely!

Keston Combi 55 error E12

Hi All,

I have a combi boiler from Keston model 55. I bought it 5 years ago and no problem with it till today. It switched off, I restarted, but it constantly shows E12. What does it mean? Is it serious? Can I fix it myself?


Hi Ken

E12 means that “thermal fuse blown or flue overheat thermostat activated”. You will need to replace both. Detailed replacement procedure is provided here in the “troubleshooting” section, and spare parts can be bought in a shop, but you should remember that only qualified – GasSafe Registered people can work on boilers.


Keston Combi C36 error E03


I have Keston Combi condensing boiler model c36, it is 7 years old and nowadays it switches itself off daily displaying message/error code E03. I checked in user manual and it means: overheat lockout mode. Does anyone know what need to be replaced and what is the cost of doing it yourself/using Keston service?


Hi John

Your problem is either very simple to fix- check if the pump is not blocked or/and what may cause lack of circulation. Or it is sth much serious  and will require checking the whole boiler/system. If it is just a pump failure cost wouldn’t be high- as not more than 2 hours are needed to complete it plus the pump cost- use rather Keston service if you have no experience with repairing boilers yourself. If however the fault is more serious I would advice purchasing new boiler.



Keston C130 fail to start

Hi All

I have Keston boiler model C130, and recently it is not starting properly. The whole starting process takes about 20 min. During this time the red lamp illuminates changing to green whenever boiler starts to light. The end result- well sometimes it starts and sometimes not. When not I restart the boiler and start the process again. Can someone advice any permanent solution?


Hi Jake

Sometimes old condensing boilers fail to fire because pressure switch breaks,  but in those cases you would hear a characteristic ‘buzzing’ noise. This noise never occurs when the boiler fires correctly and in normal operation (boiler fires, ignites, heats water and then stops).  If that is the case with your boiler, replacing the pressure switch will solves  the issue for next couple of years.