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Keston Fault Codes
Select a fault code to see its meaning, common causes and how to fix it.
C36, C40 & C55 combi codes
- E00 The E00 code means the boiler's control board is receiving a flame-detection signal at a time when the burner has not… Read more →
- E01 The E01 code appears on Keston C36 boilers (note: the equivalent fault on C40 and C55 models is E02) when the boiler… Read more →
- E02 The E02 code on Keston boilers is an ignition-related lockout, but its precise meaning differs slightly depending on… Read more →
- E03 The E03 code on Keston boilers does not have a single universal meaning — its interpretation depends on which model you… Read more →
- E04 The E04 code on a Keston boiler is a status notification rather than a fault with a specific component. It appears when… Read more →
- E05 The E05 code is a lockout fault on Keston boilers, but its precise meaning varies by model. On the Keston C36 combi,… Read more →
- E07 The E07 code means your Keston boiler has detected a fan failure — either the fan is not spinning at all, or it is not… Read more →
- E08 The E08 code on a Keston boiler signals one of two closely related problems: a flame circuit error pointing to a… Read more →
- E09 The E09 code on a Keston boiler indicates a valve drive error — the boiler's control system has detected that the gas… Read more →
- E10 The E10 code on a Keston boiler signals that the control board (PCB) has detected an internal error and cannot operate… Read more →
- E11 The E11 code indicates that your Keston boiler's control board has detected an internal electronics fault. In plain… Read more →
- E18 The E18 code on a Keston boiler signals that the water temperature in the flow pipe has climbed beyond safe operating… Read more →
- E19 The E19 fault code on Keston boilers indicates that the temperature of the water returning from the heating circuit… Read more →
- E23 The E23 fault code on a Keston boiler signals a water filling error. In plain terms, the boiler has detected a problem… Read more →
- E24 The E24 code appears on Keston boilers — most notably the C36 — when the system water pressure has dropped enough to… Read more →
- E26 The E26 fault on Keston boilers — most commonly the C36 Combi — is primarily a water pressure loss warning. The… Read more →
- E28 The E28 fault code on a Keston boiler indicates that the boiler's fan has failed to operate correctly. When the boiler… Read more →
- E30 The E30 fault code on Keston boilers signals a problem that varies slightly by model. On the C40 and C55 — the most… Read more →
- E31 The E31 code signals a problem with the flow temperature sensing circuit — the part of the boiler that monitors how hot… Read more →
- E32 The E32 fault code signals that a temperature sensor has reported an electrically invalid reading — specifically a… Read more →
- E33 The E33 code points to a problem with the domestic hot water (DHW) thermistor circuit — the sensor responsible for… Read more →
- E34 The E34 code has two distinct meanings depending on which Keston model you own — so the first step is always to confirm… Read more →
- E35 The E35 code appears when your Keston boiler detects a problem with the incoming electrical supply and locks out as a… Read more →
- E36 The E36 fault code on Keston boilers indicates that the control board has detected an open circuit on the flow (outlet)… Read more →
- E37 The E37 code appears on Keston boilers when the control system detects that the central heating water pressure has… Read more →
- E38 The E38 code on a Keston boiler signals a reset key fault — meaning the boiler's internal diagnostics have detected a… Read more →
- E40 The E40 fault code on Keston boilers signals that the system water pressure has climbed above the acceptable upper… Read more →
- E41 The E41 code indicates that the boiler's fascia (the front control panel) and the main control box (PCB) have lost… Read more →
- E43 The E43 fault code indicates that the Keston boiler's control system has detected a short circuit in the return pipe… Read more →
- E44 The E44 code on Keston boilers signals that the system water pressure has fallen below the acceptable threshold —… Read more →
- E45 The E45 code on a Keston boiler indicates that the control board has detected a short circuit in the flue sensor… Read more →
- E67 The E67 code appears on Keston Qudos boilers when the system water pressure drops below 0.4 bar — the minimum threshold… Read more →
- E99 The E99 code on a Keston boiler signals a communication breakdown between the front fascia (display panel) and the… Read more →
S30 system boiler codes
- C0 The C0 fault code on a Keston boiler signals that the PCB (printed circuit board) has been unable to successfully… Read more →
- C2 The C2 code on a Keston boiler indicates a BCC fault — a problem with the Boiler Chip Card (BCC). The BCC is a small… Read more →
- F1 The F1 code on a Keston S30 system boiler means the boiler has detected that the water pressure in your central heating… Read more →
- F2 The F2 code on a Keston boiler signals a flame loss event — the boiler attempted to burn but the flame either failed to… Read more →
- F3 The F3 fault code on a Keston boiler indicates a problem with the flue fan. Specifically, the boiler's PCB has detected… Read more →
- F4 The F4 fault code on Keston boilers indicates a problem with the flow thermistor — the NTC temperature sensor that… Read more →
- F5 The F5 fault code on a Keston boiler signals a problem with the return thermistor — a temperature sensor fitted to the… Read more →
- F6 The F6 fault code on a Keston boiler signals that the external (outdoor) temperature sensor has stopped communicating… Read more →
- F7 The F7 fault code on Keston boilers signals that the mains electrical supply reaching the boiler has dropped below the… Read more →
- F9 The F9 code on Keston boilers — most notably the S30 system boiler range — signals that the boiler's PCB (Printed… Read more →
- L1 The L1 fault code on a Keston boiler indicates that the boiler has detected either an excessively high flow temperature… Read more →
- L2 The L2 fault code on Keston boilers indicates a flame loss lockout — the boiler's flame detection system has confirmed… Read more →
- L5 The L5 code on a Keston boiler signals that the control board has detected a problem with the return thermistor — the… Read more →
- L6 The L6 code on a Keston boiler indicates a false flame lockout. This means the boiler's control system has detected a… Read more →