BoilerFaultCodesThe 6 most common faults
01
F22 High DIY-safe
Your boiler has stopped working because the water pressure inside the system is too low.
What to try first
Locate the filling loop, which is usually a flexible silver hose connected under your boiler.Open the valves at both ends of the hose to allow water into the system.Monitor the boiler's pressure gauge until it reaches between 1.0 and 1.5 bar, then securely close both valves.
02
F28 High Engineer
Your boiler is trying to start but cannot light the flame, which means you currently have no heating or hot water.
Full guide for F2803
F00 High Engineer
Your boiler has lost the ability to read the temperature of the water circulating through your heating system, so it has shut itself down to prevent it from overheating.
Full guide for F0004
F01 High Engineer
Your boiler has lost the ability to measure the temperature of the water returning to it, so it has shut down as a precaution to prevent overheating.
Full guide for F0105
F10 High Engineer
Your boiler has lost the ability to accurately measure the temperature of the water used for your heating, so it has shut down to prevent any damage.
Full guide for F1006
F11 High Engineer
Your boiler has lost the ability to accurately measure the temperature of the water coming back into it, so it has shut down to prevent overheating.
Full guide for F11on the Heatline Monza
Filling loopPressure relief valvePressure sensorIgnition electrodeGas valvePCB
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