26 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 →
Tap any card for details
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 is currently in standby mode and is working correctly, simply waiting for a demand for heating or hot water.
Your boiler is automatically adjusting its power levels, which is a normal part of its operation rather than a functional breakdown.
Your boiler is failing to light the flame needed to produce heat and hot water.
Your boiler has detected that it is running too hot and has automatically turned itself off to prevent any damage.
Your boiler has detected an issue with the ventilation system that clears away exhaust fumes, so it has safely shut itself down to prevent any risk.
Your boiler has stopped working because the water pressure inside your heating system has dropped too low to operate safely.
Your boiler has lost the ability to accurately measure the temperature of the water used for your radiators, causing it to shut down for safety.
Your boiler is currently unable to read the water temperature returning from your radiators, so it has shut down to prevent overheating.
Your boiler has stopped working because the water pressure inside the heating system has dropped too low.
Your boiler has detected that the water inside is not circulating correctly, meaning it is getting too hot in one part of the system while remaining cold in another.
Your boiler's temperature sensors have been swapped over, meaning it cannot correctly measure the heat of the water circulating through your system.
Your boiler is struggling because the internal fan that clears out exhaust gases isn't spinning at the correct speed, so the system has shut down for safety.
Your boiler's computer memory has encountered a glitch or configuration error that is preventing it from starting up correctly.
Your boiler has detected an issue with the flame and has safely shut itself down to prevent any risk.
Your boiler is struggling to talk to your room thermostat or remote control unit, causing the heating system to stop responding to your temperature settings.
Your boiler has detected a flame inside when it should be switched off, which prevents it from operating safely.
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 is operating normally and the burner is currently lit, which is exactly what should be happening when you have the heating or hot water turned on.
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 is struggling because it cannot detect enough water flowing through the system to safely turn on your heating or hot water.
Your boiler is struggling to push water around your radiators and taps because it has detected air trapped inside or the internal pump has failed.
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.
BoilerFaultCodes