BoilerFaultCodesThe 4 most common faults
01
Lockout High DIY-safe
Your boiler has stopped working and locked itself out for safety because it failed to ignite properly.
What to try first
Check that your gas supply is working by testing another gas appliance like a hob.Locate the reset button (usually a small button or switch on the front panel).Press and hold the reset button for about 5 seconds, then release to see if the boiler fires up.
02
Blocking - Mains Frequency incorrect or Air Switch Fault >1 min. or Reset button held in to force a restart High Engineer
Your boiler has temporarily stopped working because it has detected an issue with the air flow inside or the reset button has been held down for too long.
Full guide for Blocking - Mains Frequency incorrect or Air Switch Fault >1 min. or Reset button held in to force a restart03
Earth Fault or Mains Reversal High Engineer
Your boiler has detected an issue with the electrical wiring or power supply, causing it to safely lock out and stop working.
Full guide for Earth Fault or Mains Reversal04
Blocking - Mains Frequency incorrect or Air Switch Fault High Engineer
Your boiler has stopped working because it has detected an issue with the electricity supply frequency or a problem with the internal air pressure switch.
Full guide for Blocking - Mains Frequency incorrect or Air Switch Faulton the Baxi Suprima 60
PCBSpark generatorIgnition electrodeAir pressure switchFlue terminalFused Spur
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