BoilerFaultCodesThe 6 most common faults
01
1 High DIY-safe
Your boiler is trying to fire up for heating or hot water, but the burner isn't catching.
What to try first
Check your oil supply to ensure you have not run out of heating oil.Verify that the oil supply valve to the boiler is fully open.Press the reset button on the burner control box once to see if it restarts.
02
3 High DIY-safe
Your boiler is trying to fire up, but the oil burner is failing to catch a flame and is shutting down for safety.
What to try first
Check your oil tank to ensure you have not run out of heating oil.Locate the lockout reset button on the burner, press it once firmly, and wait to see if the boiler restarts.Check if any oil supply valves or fire valves have been accidentally tripped or closed.
03
2 High Engineer
Your boiler is trying to fire up for heating or hot water, but the burner isn't catching, so it has safely locked itself out.
Full guide for 204
4 High Engineer
Your boiler's burner tries to start up, but it immediately gives up and shuts down for safety.
Full guide for 405
5 Emergency Engineer
Your boiler is struggling to light smoothly, resulting in a loud bang or rumble when the flame finally catches.
Full guide for 506
6 Medium Engineer
Your boiler is repeatedly switching itself on and off instead of staying lit to heat your home.
Full guide for 6on the Grant Vortex Eco External Wall Hung
PhotocellOil burner nozzleControl boxIgnition electrodesPhotocell (Flame detector)Oil nozzle
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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