BoilerFaultCodesThe 3 most common faults
Your boiler has detected an issue with the airflow system, which is preventing the burner from lighting for safety reasons.
Why it happens: This fault occurs when the boiler's safety sensors cannot confirm that the fan is successfully pushing exhaust fumes out of the flue. The most common reasons are a buildup of debris in the fan or air tubes, or the mechanical switch itself failing to register the flow of air. Until the boiler is certain it can vent gases safely, it will prevent the burner from firing.
Full guide for APS neon litYour boiler is struggling to maintain a strong flame, which is why it keeps turning off or failing to heat up properly.
Why it happens: This fault occurs when the boiler's internal sensor detects that the flame is too weak or unstable to safely heat the system. The most common reasons are a worn-out ignition electrode that can't spark correctly or a gas valve that isn't delivering the right amount of fuel to stay lit.
Full guide for Low neon lightYour boiler's status light indicates it is running at its maximum heating power, but if the light remains off while the boiler is struggling, there may be an internal electrical communication fault.
Why it happens: This occurs when the boiler is commanded to run at its highest heat output but the electrical signal fails to register. The most common reason is a mechanical failure in the high/low switch or a break in the wiring that prevents the system from confirming the flame level. This results in the boiler being unable to modulate its power correctly to meet the demands of your heating system.
Full guide for High neon lighton the Glow-worm EnergySaver
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 Glow-worm 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