29 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: CD24R
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's internal thermometer is providing confusing information, so it has turned itself off as a precaution to prevent overheating.
Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.
Your boiler has detected a faulty internal sensor that monitors water temperature, causing the heating system to stop working for safety.
Your boiler has detected a problem with the internal thermometer that monitors water temperature, causing the heating to stop working as a safety precaution.
Your boiler is failing to light the burner, meaning it cannot provide you with any heating or hot water.
Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.
Your boiler has detected an issue with the ventilation system that clears away exhaust gases, so it has automatically shut down for your safety.
Your boiler has stopped working because the water pressure in the central heating system has dropped too low.
Your boiler has stopped providing heating and hot water because it is having trouble reading the temperature of the water moving through the system.
Your boiler is struggling to detect the temperature of your hot water supply, so it has safely shut down the taps to prevent overheating.
Your boiler has detected a problem with the sensor that monitors exhaust gases, and it has stopped working as a safety precaution.
Your boiler has detected that the water pressure is too low for the system to operate safely.
Your boiler has detected that the water leaving the unit is getting too hot, causing it to shut down for safety.
Your boiler has detected that the water returning from your radiators is getting too hot, usually because the water isn't circulating properly through the system.
Your boiler has detected that water is not circulating through the system correctly, causing a heat imbalance that has prompted the unit to shut down for safety.
Your boiler is struggling to accurately measure the temperature of the water returning to it, which causes it to stop working as a safety precaution.
Your boiler has stopped working because it cannot properly clear exhaust gases, which is a necessary safety step before it can produce heat.
Your boiler has stopped working because the waste water pipe is either blocked or full, often caused by the outdoor section of the pipe freezing in cold weather.
Your boiler's internal computer is experiencing a software-related communication failure, preventing the appliance from operating safely.
Your boiler is failing to detect the flame that heats the water, causing the system to shut down for safety.
Your boiler has detected an electrical issue with the component that controls the gas supply, preventing it from firing up for heating or hot water.
Your boiler has lost its digital connection to the wall-mounted thermostat or remote control unit, meaning it does not know when to turn your heating on or off.
Your boiler is not receiving the correct amount of electrical power to function properly, which is usually caused by an external power dip or a faulty internal circuit board.
Your boiler started to heat up but the flame went out unexpectedly while it was running.
Your boiler has stopped working because the amount of water in your central heating system is too low.
Your boiler is repeatedly struggling to keep its flame lit and has shut down as a safety precaution to prevent unburnt gas from building up.
Your boiler is currently working as expected and the burner is firing to provide heating or hot water.
Your boiler has lost power or has an internal electrical fault, meaning it cannot provide any heating or hot water until an electrical issue is resolved.
Your boiler is receiving power correctly and is currently in its normal standby state.
BoilerFaultCodes