7 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: CD28C
This boiler uses LED flash patterns
Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →
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Your boiler has lost the ability to accurately measure its internal temperature, so it has safely shut down to prevent overheating.
Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.
Your boiler's fan is running continuously at top speed, which indicates the internal computer has detected a safety concern and is trying to vent the system.
Your boiler's electronic control panel is experiencing an internal fault, causing a warning light to stay on and likely preventing your heating or hot water from working.
Your boiler's water pump is running constantly, which often indicates the system is failing to detect that it has successfully reached the required temperature or is struggling to circulate water properly.
Your boiler has stopped working because it failed to ignite, so it has automatically shut down for safety.
Your boiler is attempting to light but is struggling to complete the ignition process, preventing your heating or hot water from working correctly.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes