BoilerFaultCodesThe 5 most common faults
01
IGNITION LOCKOUT INDICATOR High DIY-safe
Your boiler has stopped working because it failed to light the flame, which usually happens due to a blocked flue, a frozen pipe, or a gas supply issue.
What to try first
Check that your gas supply is turned on at the meterEnsure any other gas appliances are working to rule out a network supply issuePress the reset button once and wait for the boiler to cycle
02
OVERHEAT LOCKOUT INDICATOR High Engineer
Your boiler has switched itself off because it got too hot, which is a safety feature designed to prevent overheating damage.
Full guide for OVERHEAT LOCKOUT INDICATOR03
Overheat LED High Engineer
Your boiler has detected that it is running too hot and has automatically shut itself down to prevent any damage or safety hazards.
Full guide for Overheat LED04
Ignition Lock-out neon High Engineer
Your boiler has stopped working because it failed to light the flame properly, so it has shut itself down for safety.
Full guide for Ignition Lock-out neon05
Overheat LED illuminated High Engineer
Your boiler has detected that it is running too hot and has automatically shut down to prevent damage, meaning you currently have no heating or hot water.
Full guide for Overheat LED illuminatedon the Halstead Best 20
Ignition electrodeGas valvePrinted Circuit Board (PCB)Flame rectification probeOverheat thermostatPrimary pump
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 Halstead 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