BoilerFaultCodesThe 6 most common faults
01
F.10 High Engineer
Your boiler's internal thermometer has developed a fault and can no longer tell how hot the water is, causing the system to shut down for safety.
Full guide for F.1002
Connection High Engineer
Your boiler's internal control board and the display panel have lost touch with each other, meaning the boiler cannot receive your commands to turn on.
Full guide for Connection03
F3 High Engineer
Your boiler has detected that the internal mechanism responsible for clearing waste gases is not operating correctly, so it has safely shut down to prevent unsafe operation.
Full guide for F304
F4 High Engineer
Your boiler is struggling to keep the flame lit while it is running, causing it to shut down for safety.
Full guide for F405
F6 High Engineer
Your boiler has lost the signal from the sensor that monitors the temperature of the water being sent to your radiators, causing it to stop heating.
Full guide for F606
F14 High Engineer
Your boiler is struggling to control the internal fuel supply, meaning it cannot safely ignite or maintain a flame to heat your home.
Full guide for F14on the Glow-worm Ultracom hxi
Flow temperature sensor (NTC thermister)Internal wiring loomMain Printed Circuit Board (PCB)User Interface BoardInternal Wiring LoomFan assembly
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