BoilerFaultCodesThe 6 most common faults
01
1 High Engineer
Your boiler has detected an electrical short circuit in its low-voltage control system, which causes it to shut down for safety.
Full guide for 102
2 High Engineer
Your boiler is trying to start up, but it is failing to ignite or stay lit after a couple of attempts.
Full guide for 203
4 High Engineer
Your boiler has experienced a power drop while attempting to lock out for a safety fault.
Full guide for 404
5 High Engineer
Your boiler is not detecting proper airflow or exhaust movement, which temporarily stops it from running safely.
Full guide for 505
6 High Engineer
Your boiler has detected an internal memory error within its main control unit, causing it to temporarily lock out for safety.
Full guide for 606
7 High Engineer
Your boiler has stopped working because an internal electrical fuse has blown, cutting power to essential components.
Full guide for 7on the Remeha W40
Internal wiring harnessPCB (Printed Circuit Board)External controlsIgnition electrodeGas valveIonisation probe
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 Remeha 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