18 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Grant VortexBlue
This boiler uses indicator light combinations
Note which lights are on, off, or flashing and at what speed. Match the combination to the cards below. Do not reset until you have noted the pattern. How to read fault codes →
Tap any card for details
Your boiler's electronic brain is unable to communicate correctly, which has caused it to lock out to prevent unsafe operation.
Your boiler's main control computer is experiencing an error, which has caused it to stop the burner from operating to prevent further issues.
Your boiler's electronic brain is malfunctioning and needs to be replaced by a professional to get your heating system running again.
Your boiler's temperature sensor is failing to communicate properly, which is preventing it from heating your water correctly.
Your boiler's internal control brain is experiencing an electronics failure and can no longer reliably signal the system to move hot water around your home.
Your boiler is struggling to detect the temperature of your hot water supply, which means it will likely stop heating your water until a faulty sensor or internal control board is replaced.
Your boiler is struggling to accurately measure the temperature of the water inside its internal storage tank, which means it may fail to provide hot water correctly.
Your boiler's electronic brain is experiencing a minor internal error and needs a service visit to replace a faulty control component.
Your boiler has detected an internal light source that shouldn't be there, so it has safely shut itself down to prevent ignition.
Your boiler has detected light inside the combustion chamber when it should be dark, causing it to lock itself out as a safety precaution.
Your boiler has stopped working because the amount of water in your heating system is too low to run safely.
Your boiler has detected a signal that it is already burning fuel even though it has not been told to start, so it has safely shut itself down to prevent an unsafe situation.
Your boiler has failed to start after several repeated attempts and has now automatically shut down for safety to prevent fuel buildup.
Your boiler has disabled itself for safety after multiple failed attempts to start the burner, and it now requires a specific cooling period or a professional reset to clear the lock.
Your boiler has detected an internal electrical issue affecting the fuel delivery system, which is preventing it from firing up safely.
Your boiler is unable to safely vent exhaust gases because the air-moving fan inside the unit has failed or lost its electrical connection.
Your boiler has stopped itself from running as a safety precaution because the fuel failed to ignite properly.
Your boiler has detected an issue preventing it from lighting and has shut down for safety; it needs a manual reset to try and start again.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes