BoilerFaultCodesThe 4 most common faults
01
Lock-out High DIY-safe
Your boiler has stopped working to protect itself and needs to be restarted, though it may take a few attempts to get it running again.
What to try first
Check your external oil supply tank to ensure you have enough fuel and that any isolation valves are open.Locate the reset button on the boiler casing (or the burner unit) and press it once firmly.Wait for the boiler to attempt an ignition cycle; if it fails again, do not force the reset more than three times.
02
Lock-out (Red neon) High Engineer
Your boiler has stopped working because the flame inside failed to light or stay on.
Full guide for Lock-out (Red neon)03
10 Emergency Engineer
Your boiler is struggling to vent exhaust gases properly when it starts up, which could lead to fumes building up in your home.
Full guide for 1004
12 Emergency Engineer
Your boiler is allowing exhaust fumes to escape into your home, which is a serious safety concern that must be addressed immediately.
Full guide for 12on the Grant Vortex
PhotocellIgnition electrodesFuel pumpControl boxOil nozzleFlue terminal
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 Grant 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
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