BoilerFaultCodesThe 6 most common faults
01
1 red flash High DIY-safe
Your boiler has detected that it is getting too hot or the water isn't moving through the system properly, causing it to shut down for safety.
What to try first
Check that your radiator valves are openEnsure your system water pressure is within the green zone (usually 1.0 to 1.5 bar)Perform a reset by turning the control knob to 'R' or the reset position for five seconds
02
2 red flashes High DIY-safe
Your boiler has become too hot and has automatically shut down to prevent damage or unsafe operation.
What to try first
Check that all radiator valves are open and not blocked by furnitureEnsure the system water pressure is between 1 and 1.5 barPress the reset button or turn the control knob to 'R' for five seconds
03
3 red flashes High DIY-safe
Your boiler is failing to light the burner after several attempts, which means your heating and hot water will not work.
What to try first
Check that your gas prepayment meter has credit (if applicable)Ensure all external gas isolation valves are turned to the 'on' positionPress and hold the reset button or turn the control knob to 'R' for five seconds
04
128 High Engineer
Your boiler started to provide heat but the flame went out unexpectedly while it was running.
Full guide for 12805
4 red flashes High Engineer
Your boiler has stopped working because the fan that helps remove exhaust gases is not spinning correctly or communicating with the control board.
Full guide for 4 red flashes06
5 red flashes High Engineer
Your boiler's internal memory chip has developed a communication fault, preventing the system from running safely.
Full guide for 5 red flasheson the Baxi Bermuda
NTC Temperature SensorCirculation PumpOverheat ThermostatThermistor (NTC Sensor)Ignition ElectrodeGas Valve
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