BoilerFaultCodesThe 6 most common faults
01
10 High Engineer
Your boiler is struggling to clear exhaust gases safely because it cannot confirm that the internal fan is moving air properly, so it has shut down to prevent unsafe operation.
Full guide for 1002
12 High Engineer
Your boiler is attempting to light but failing to stay on, meaning you currently have no heating or hot water.
Full guide for 1203
13 High Engineer
Your boiler is struggling to clear exhaust gases safely, so it has turned itself off to prevent a build-up of fumes.
Full guide for 1304
14 High Engineer
Your boiler is struggling to clear exhaust gases out through the flue, so it has safely shut down to prevent any risk of fumes entering your home.
Full guide for 1405
15 High Engineer
Your boiler has stopped working because it cannot safely clear waste gases through the flue.
Full guide for 1506
16 High Engineer
Your boiler has stopped working because it cannot properly clear exhaust gases, which has triggered a safety shutdown to prevent dangerous fumes from building up.
Full guide for 16on the Heatline Sargon
Air pressure switchFlue fan unitVenturi tubeGas valveIgnition electrodePCB
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 Heatline 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