Keston
Keston C36 Combi
Combi Boiler
36kW
2005-2018
ErP A
40 fault codes
<p>The Keston C36 Combi is a combi boiler from Keston, available at 36kW output. Produced 2005-2018.</p>
Keston C36 Combi Fault Codes 40
Code
Description
Severity
Type
E01
Ignition Failure — 5 Attempts
The boiler has attempted to light 5 times and failed. The most common Keston fault code.
Medium
DIY
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E02
False Flame Detected (C36/CSI)
The boiler's ionisation circuit is detecting a flame when none should be present. Possibly a power…
High
Engineer
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E03
Boiler Overheat
The boiler has overheated — check for closed valves, air in system, or incorrect water pressure.
High
Engineer
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E05
Fan Failure
The boiler cannot detect fan rotation — the fan may be seized or have a wiring…
High
Engineer
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E07
Flue Overheat
The flue temperature has exceeded safe limits. The flue temperature should be no more than 10°C…
High
Engineer
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E08
Flame Circuit Error
There is a fault in the flame monitoring circuit — possibly the control box.
High
Engineer
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E09
Gas Valve Drive Error
The gas valve or control box has a fault — the valve is not responding to…
High
Engineer
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E18
Flow Overheat (C40/C55)
On Keston C40 and C55 boilers, E18 indicates the flow temperature has exceeded safe limits. Check…
High
Engineer
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E23
Water Filling Error
The water pressure sensor has detected an issue during the automatic filling sequence.
Medium
Engineer
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E24
Water Pressure Lost 4 Times in 24 Hours
The system has lost pressure 4 times within 24 hours — indicating a possible leak.
High
Engineer
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E26
Flame Drop Out
The boiler flame has dropped out during operation. Check for flue obstruction, blocked condensate drain, or…
Medium
DIY
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E30
Flow Sensor Short Circuit
The flow temperature sensor has short-circuited.
Medium
Engineer
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E31
Flow Sensor Open Circuit
The flow temperature sensor circuit is open — the sensor is not connected or has failed.
Medium
Engineer
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E37
Water Pressure Error
The water pressure is too low — increase system pressure using the filling loop.
Low
DIY
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E40
Water Pressure Too High
The system water pressure is too high — above 3 bar.
Medium
Engineer
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E43
Return Sensor Short Circuit
The return temperature sensor has short-circuited.
Medium
Engineer
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E44
Return Sensor Open Circuit (C55)
The return temperature sensor circuit is open on the C55 boiler.
Medium
Engineer
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E44 (C36)
Low Water Pressure (C36)
On the Keston C36, E44 specifically indicates low water pressure (this is different from E44 on…
Low
DIY
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