BoilerFaultCodesThe 6 most common faults
01
Mains LED off High DIY-safe
Your boiler has lost all power and is completely shut down, meaning it cannot provide any heating or hot water.
What to try first
Check your home's consumer unit (fuse box) to ensure the boiler's circuit breaker hasn't tripped.Ensure the fused spur switch located near the boiler is turned on.Check that the fuse inside the fused spur switch has not blown.
02
Ignition Lockout High Engineer
Your boiler has stopped working because it couldn't light the flame, so it has safely shut itself down to prevent gas from building up.
Full guide for Ignition Lockout03
Mains LED flashing High Engineer
Your boiler's control panel is not receiving a signal, which is preventing it from firing up to provide your heating and hot water.
Full guide for Mains LED flashing04
Lockout LED continuously on High Engineer
Your boiler has stopped working because it failed to light the flame, which means you currently have no heating or hot water.
Full guide for Lockout LED continuously on05
Fan not running High Engineer
Your boiler has stopped working because it cannot clear stale air and bring in fresh air needed for safe operation.
Full guide for Fan not running06
Lockout will not reset High Engineer
Your boiler has detected that it is dangerously overheated or has run without enough water and will not restart until it has cooled down completely.
Full guide for Lockout will not reseton the Baxi 800 Heat (range)
Fused spurPCBTransformerIgnition electrodeGas valveIgnition lead
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