BoilerFaultCodes
Keston Boiler Fault Codes
539 fault codes across 16 Keston boiler models — explained in plain English.
UK premium condensing boiler brand, now part of Baxi Group.
Just want the most common Keston problems?
The top 8 faults across the whole Keston range — causes, DIY checks, repair costs.
High-severity Keston fault codes
F0 F7 F9 L5 L6
Your boiler's main control computer is missing a vital activation chip, which means the system cannot start up or provide any heat.
S30
Your boiler has detected that the electricity supply coming into your home is at a lower voltage than it needs to operate safely.
S30
Your boiler's internal computer has encountered a critical error and cannot communicate with the rest of the system.
S30
Your boiler has been manually reset too many times in a short period and has locked itself out to prevent further damage or safety issues.
S30
Your boiler thinks it sees a flame even though it isn't currently trying to light, causing the system to shut down for safety.
S30
All models
16 Keston boiler models
S30
System
C36
System Discontinued
C55
System Discontinued
Heat 45
System Discontinued
Heat 55
System Discontinued
Heat 80
System Discontinued
System S30
System
System S40
System
Celsius 25
System Discontinued
Celsius 30
System Discontinued
C36p
Combi
C40
System Discontinued
C90 / C110
System Discontinued
K170
System Discontinued
K50, K60, K80
System Discontinued
R-sm 20 FB
Regular Discontinued