25 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Compact A
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 is working normally and is receiving power with no faults detected.
Your boiler is working correctly and is simply waiting for a request from your thermostat or hot water tap to start heating.
Your boiler has likely overheated or has an issue with its internal fan system, causing it to shut down for safety.
Your boiler is currently running in a special engineer's test mode used to check emissions and is not experiencing a mechanical breakdown.
Your boiler is struggling to keep a flame alive because it is not getting the correct gas supply or the exhaust passageway is obstructed.
Your boiler is struggling to accurately detect the temperature of the water being heated for your taps, which means it may fail to provide hot water or heat it to the wrong temperature.
Your boiler has detected a general internal error and has locked itself out for safety, meaning your heating and hot water will not work until it is reset or repaired.
Your boiler has paused temporarily because it is waiting for a part to cool down or for a system sensor to detect the correct reading before restarting.
Your boiler has no power and is completely unresponsive, meaning the heating and hot water will not work.
Your boiler has experienced a safety lockout and has shut itself down to prevent damage.
Your boiler is in a temporary standby mode because it has detected a minor issue, such as low water pressure or a momentary sensor error.
Your boiler is in normal standby mode and is simply waiting for you to turn on the heating or hot water.
Your boiler has lost water pressure and has shut itself down as a safety precaution to prevent damage.
Your boiler is working normally and is currently heating your radiators or providing hot water.
Your boiler has entered a safety lockout mode due to a critical internal fault or an ignition failure.
Your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.
Your boiler has stopped working because the water pressure is too low for the system to run safely.
Your boiler has stopped working because it failed to light properly or cannot detect a flame.
Your boiler has detected a safety-related issue with its internal components or airflow and has locked itself down to prevent damage.
Your boiler has detected a fault with its internal temperature sensor, preventing it from heating your water and radiators safely.
Your boiler is currently in a manual testing mode often used by engineers and is not experiencing a functional fault.
Your boiler has detected a problem with the hot water system, meaning you likely have no hot water even if your heating still works.
Your boiler is struggling to accurately monitor the temperature of the water being used for your heating because a temperature probe is sending incorrect signals or has a poor electrical connection.
Your boiler is currently running in a special engineer-only testing mode used to check combustion levels, meaning it is not in its normal operating state.
Your boiler has detected a problem with the temperature sensor that controls your hot water, meaning you likely have no hot water or the temperature is inconsistent.
BoilerFaultCodes