BoilerFaultCodesThe 4 most common faults
01
10.4 High DIY-safe
Your boiler has switched itself off to prevent overheating, likely because the internal temperature has become too high.
What to try first
Turn off the power supply to the boiler and let it cool down for at least 30 minutes.Check that all your radiator valves are open and not turned off.Press the manual reset button, which is usually found behind the front panel or at the bottom of the unit.
02
10.1 High Engineer
Your boiler is unable to start the small flame needed to fire up the main heating system, which means you have no heating or hot water.
Full guide for 10.103
10.2 High Engineer
Your boiler's pilot light is failing to stay on, which prevents the main burner from firing and heating your home.
Full guide for 10.204
10.3 High Engineer
Your boiler has a flame for the pilot light, but the main heating burner is failing to ignite, meaning you won't have any heating or hot water.
Full guide for 10.3on the Myson Economist WM
Limit ThermostatCirculation PumpOverheat SensorThermocoupleGas valveSpark electrode
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 Myson 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