BoilerFaultCodesThe 6 most common faults
01
F5 High Engineer
Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.
Full guide for F502
F1 High Engineer
Your boiler has failed to ignite and has shut itself down as a safety precaution because it cannot start the heating process.
Full guide for F103
F.10 High Engineer
Your boiler has detected an electrical fault in the sensor that monitors the temperature of the water leaving the unit, causing it to stop working to stay safe.
Full guide for F.1004
F.11 High Engineer
Your boiler has detected a faulty reading from the sensor that monitors the temperature of the water returning to the unit, causing it to shut down to prevent damage.
Full guide for F.1105
F.13 High Engineer
Your boiler has detected a faulty sensor reading in the pipework that carries water back from your radiators, preventing it from heating your home correctly.
Full guide for F.1306
F.14 High Engineer
Your boiler has detected a faulty sensor that is incorrectly measuring the temperature of the water moving through your heating system, causing it to shut down to prevent damage.
Full guide for F.14on the Glow-worm Flexicom CXi
PumpHeat exchangerNTC thermistorDiverter valveIgnition 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 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