BoilerFaultCodesThe 6 most common faults
01
1 flash green High Engineer
Your boiler has detected that the water inside it is getting too hot, too quickly, or is unable to circulate properly, so it has shut down to prevent damage.
Full guide for 1 flash green02
2 flashes green High Engineer
Your boiler has received a signal from an external control, such as a smart thermostat or a safety device, telling it to turn off.
Full guide for 2 flashes green03
3 flashes green High Engineer
Your boiler has stopped because the flame inside has gone out and it cannot get it to stay lit.
Full guide for 3 flashes green04
4 flashes green High Engineer
Your boiler's internal computer is struggling to communicate with its own parts, meaning it has safely shut down until it can 'talk' to itself properly again.
Full guide for 4 flashes green05
5 flashes green High Engineer
Your boiler's internal computer is experiencing a software or communication error and has stopped working to prevent any potential damage.
Full guide for 5 flashes green06
6 flashes green High Engineer
Your boiler has detected an internal electronic error within its main control system that is preventing it from starting safely.
Full guide for 6 flashes greenon the Baxi 800 Heat
Central Heating PumpPlate Heat ExchangerDiverter ValveExternal programmerSmart thermostatWiring link
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Baxi shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue
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