Keston Boiler Error Codes, Causes & How To Fix

James Elston
Written by James Elston
Updated on 17th October 2023
Posted on 20th September 2023
Keston Boiler Error Codes, Causes & How To Fix

Keston boiler error codes and faults: What they mean and how to fix them

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When your Keston boiler isn’t working how it should, you need to get it up and running as soon as possible. The error code displayed on your boilers control panel provides you with some information on what might be going on.

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Now, error codes aren’t exclusive to Keston boilers; problems with the heating and hot water are displayed this way by all boiler manufacturers. New boilers and old boilers alike, things can go wrong so we’re here to help.

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Common Keston Boiler Error Codes & Faults

In this article, we’re going to focus on the codes which may appear on your Keston boiler. We’ll start with the most common codes and then finish off with the complete list.

The best combi boilers and system boilers can break, but the good news is that for some of the issues, there’s a good chance that you’ll be able to fix the problem yourself without needing to call the Keston boilers technical helpline or arrange for an engineer to come out!

How to fix error code E12

When you get the Keston boiler error code E12, it will, unfortunately, mean that an engineer needs to be called out. That’s because this code means that there has been a blown thermal fuse that needs replacing. As this requires the boiler cover to be removed, only a gas certified engineer can undertake the repair.  

If your boiler is under warranty, contact the Keston boiler repairs hotline, and they’ll arrange for an engineer to visit. If you don’t have warranty cover, we strongly recommend getting boiler cover in place before any problems happen to make sure that you don’t need to deal with unexpected repair bills.

How to fix error code E37

The Keston boiler e37 error code means a problem with the water pressure within your system. This is one which you’ll be able to sort out yourself as this simply needs more water adding to your boiler until the correct pressure is reached. For information on how to do this, check your boiler manual. Electronic copies can be found on the Keston website.

To understand more about pressure issues, our complete guide can be found here.

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How to fix error code E28

The Keston boiler error code e28 usually means that you’re not getting any hot water or heating. It’s caused by a faulty fan, and often you’ll see the boiler pump working for around five seconds and then it goes into lockdown.

This one will need an engineer to come out and, first of all, check if there is an issue with the power to the fan, and if that seems okay, then a replacement will be needed.

How to fix error code E67

The Keston boiler error code e67 means that the water pressure in your heating system is too low. This means that you need to top up the water while keeping an eye on the pressure gauge; you’re aiming for a pressure of between 1 and 2 bar.

If the pressure keeps dropping, this may be the sign of a boiler water leak, and that will need the help of an engineer to carry out a repair.

See how much a boiler service costs here which can pick up any early keston boiler problems.

All Keston Boiler Error Codes

 Take a quick look at our comprehensive list of fault codes you will find with your Keston boiler. If your issues are serious then we can also help you find out what a new boiler cost.

C36 Combi Gas Boiler Error Codes

Fault CodePossible Cause
E01Failure of the ignition
E02False flame and may be issues with the gas supply
E03Overheated boiler
E05Failure of the fan
E07Overheated flue
E08Problems with the flame circuit
E09Error with the valve drive
E10Faulty control box
E11Failure of the calibration tests for the flow and return sensors
E12 to E22Faulty control box
E23Error with the water filling process
E24Low pressure detected four times in the last 24 hours
E25Faulty control box
E26Flame dropping out
E28Faulty fan
E30Short circuit of the flow sensor
E31Open circuit within the flow sensor
E32Short circuit of the DHW sensor
E33Short circuit of the hot water sensor
E34The mains supply has dropped below 180V
E35Issues with the mains supply frequency
E37Water pressure incorrect
E38Faulty reset key
E40Water pressure too high
E41Error of communication between fascia and control box
E43Return sensor has short-circuited  
E44Open circuit on the return sensor
E45The Flue sensor has short-circuited
E46Error of communication error between the fascia and control box
E67Water pressure is below 0.4 bar
E99Short circuit of the flue sensor


S30 System Gas Boiler Error Codes

Fault CodePossible Cause
0Standby mode
CDesired temperature not yet reached
C And Burner LightOperational for hot water and heating
F And Burner LightFrost mode in operation
F0Missing boiler chip code
F6Failure of the outside sensor
F7Mains voltage too low
F9Fault within the printed circuit board
L5Too many boiler resets within 5 minutes
L6Lockout due to false flame warning
C0Fault with the boiler chip card
C2Fault with the boiler chip card
F1Water pressure too low
L1Overheating of the flow temperature
F2Loss of flame
L2Loss of flame
F3Fault with the fan
F4Fault with the flow thermistor
F5Fault with the return thermistor


Keston c40 Boiler Error Codes

Fault CodePossible Cause
EnnBoiler shut down because of a fault in the system
E00Unexpected flame has been detected
E02Faulty ignition after the boiler has been restarted
E03Faulty or disconnected gas valve
E04Boiler in lockout followed by a power reset
E11Problem with the internal electronics
E18Overheating of the flow
E19The return water has exceeded the maximum allowed temperature
E25Rapid increase of the flow temperature which exceeds the allowed parameters
E30Difference in temperature between flow and return is too high
E31Short circuit of the flow thermistor
E32Short circuit of the return thermistor
E36Open circuit on the low thermistor
E37Open circuit on the return thermistor
E44Water pressure too low


All boilers develop faults from time to time but knowing what the error code means could help you fix it yourself or get an engineer out asap.

Don’t forget that keeping up to date with your Keston boiler service schedule will also help to identify minor problems before they become critical.

There will come the point, though, where your boiler reaches the end of its life or where the cost of repairs just isn’t feasible for an old system.

There are other less known boiler manufacturers to you could explore such as Navien boiler error codes & Daikin boiler error codes so that you can see just how common these issues are with brands that don’t have as much pedigree as the main ones.

Then comes the search for a new boiler. With so many choices now available, our fixed price boiler installation service is a great place to start.

Simply provide a few details about your home and your heating requirements, and you’ll be instantly provided with great boiler deals for the perfect boiler system.

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Written by
James Elston
James Elston Director Of Boiler Central
Posted on: 20th September 2023

James Elston is our resident boiler replacement and heating expert here at Boiler Central. With over 20 years experience in the boiler installation industry, James ensures that he knows everything there is about our Gas Safe boiler installations, energy saving and home heating solutions. This can be from simply procuring the latest best combi boilers, to reviewing and ensuring that Boiler Central maintains the highest standards across our boiler installation company.

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