With a rich history dating back to 1974, Maintracts Services has been a leading provider of top-notch heating services. Our team of expert heating engineers has extensive experience in dealing with Keston boilers, offering a comprehensive range of services, including new boiler installation, maintenance, and repair. In today’s blog post, we’ll be focusing on a topic that every Keston boiler owner or technician should be familiar with: common Keston boiler error codes. These error codes can be perplexing, but fear not! We’re here to provide you with valuable insights into what these error codes mean and how to effectively troubleshoot them. So, whether you’re a homeowner, landlord, or a heating professional, join us as we unravel the mysteries of Keston boiler error codes and help you keep your heating system running smoothly.
C36 Combi Gas Boiler Error Codes
| Fault code | Possible cause |
| E01 | Ignition failure – the boiler has attempted to light 5 times and not succeeded – check the gas supply is on |
| E02 | False flame – possibly a problem with the power supply |
| E03 | Boiler overheat – check that any valves to the heating circuit have not been shut down, no air in the system and that the water pressure is correct |
| E05 | Fan failure – boiler cannot detect fan rotation – check fan operation and both connectors onto fan |
| E07 | Flue overheat – check combustion and flue temperature vs. return temperature – the flue temperature should be no more than 10C above return temperature. Possible heat exchanger fault. |
| E08 | Flame circuit error – possible control box fault |
| E09 | Valve drive error – possible gas valve or control box fault |
| E10 | Control box errors – possible faulty control box |
| E11 | The automatic test for calibration of flow and return sensors has failed – check both flow and return sensors are located on the correct pipes and are producing the correct readings |
| E12 to E22 | Control box errors – possible faulty control box |
| E23 | Water filling error – check water pressure sensor |
| E24 | Water pressure lost 4 times in 24 hours – possible leak, check system and boiler |
| E25 | Control box errors – possible faulty control box |
| E26 | Flame drop out – check for obstruction of the flue and/or air terminals, blockage/freezing of the drain pipe or a low gas supply (LPG). |
| E30 | Flow sensor short circuit – check connections to flow sensor |
| E31 | Flow sensor open circuit – check connections to flow sensor are in place |
| E32 | DHW sensor short circuit – check connections to domestic hot water (DHW) sensor |
| E33 | Domestic hot water (DHW) sensor short circuit – check connections to DHW sensor are in place |
| E34 | Mains supply voltage < 180V – may be a problem with your power supply |
| E35 | Mains supply frequency incorrect – may be a problem with the power supply |
| E37 | Water pressure error – increase water pressure |
| E38 | Reset key fault – replace fascia PCB |
| E40 | Water pressure too high |
| E41 | Communication error between fascia and control box – check cables |
| E43 | Return sensor short circuit – check connections to return sensor |
| E44 | Return sensor open circuit – check connections to return sensor are in place |
| E45 | Flue sensor short circuit – check connections to flue sensor |
| E46 | Communication error between fascia and control box – check cables |
| E99 | Flue sensor short circuit – check connections to flue sensor are in place |
S30 System Gas Boiler Error Codes
| Fault code | Possible cause |
| 0 | The boiler is in standby mode awaiting either a central heating call or hot water demand |
| C | The boiler has a call for central heating / hot water but the appliance has reached the desired temperature set on the boiler |
| C And Burner Light | The boiler is operating for central heating / hot water |
| F And Burner Light | The boiler is operating in frost mode |
| F0 | Boiler Chip Card (BCC) not fitted |
| F6 | Outside sensor failure |
| F7 | Low mains voltage |
| F9 | Printed circuit board (PCB) Fault |
| L5 | 5 boiler resets in 15 minutes |
| L6 | False flame lockout |
| C0 | Boiler Chip Card (BCC) activation fault |
| C2 | Boiler Chip Card (BCC) fault |
| F1 | Low water pressure |
| L1 | Flow temperature overheat |
| F2 | Flame loss |
| L2 | Flame loss |
| F3 | Fan fault |
| F4 | Control / No flow thermistor |
| F5 | Return thermistor |
C40 C55 Combi gas boiler
| Fault code | Possible cause |
| Enn | Fault causing a boiler shutdown |
| E00 | Flame detected when not expected – check boiler earth and probe condition |
| E02 | No ignition after restart – check gas supply, gas valve operation and ignitor electrode spark generation |
| E03 | Gas valve faulty or not connected |
| E04 | Power has been reset whilst boiler was in lockout |
| E11 | Internal electronics error – rest or replace control box |
| E18 | Flow overheat – check water circulation |
| E19 | Maximum return temperature exceeded – check circulation |
| E25 | Flow temperature increased too quickly – check water circulation |
| E30 | Difference between flow and return temperatures too high – check circulation. |
| E31 | Flow thermistor short circuit – check/replace connections/thermistor |
| E32 | Return thermistor short circuit – check/replace connections/thermistor |
| E36 | Flow thermistor open circuit – check/replace connections/thermistor |
| E37 | Return thermistor open circuit – check/replace connections/thermistor |
| E44 | Low water pressure |
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