BoilerFaultCodesThe 6 most common faults
01
10 High DIY-safe
Your boiler has stopped working because the amount of water inside your central heating system has dropped too low.
What to try first
Locate the filling loop, which is usually a silver braided flexible hose connected to two valves beneath the boiler.Open the valves slowly to allow water into the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.Close both valves tightly and ensure the filling loop is disconnected if it is a detachable type.
02
B flashing High DIY-safe
Your boiler has automatically turned itself off because it became too hot, often due to a restriction in the water flow.
What to try first
Locate the main selector switch on the front control panel.Turn the selector switch to the 'Reset' position (marked as 3).Hold it there for a few seconds and then return it to your desired winter/summer setting to see if the burner fires up.
03
02 High Engineer
Your boiler has automatically turned itself off because it has become too hot inside, likely due to a lack of water flow.
Full guide for 0204
05 High Engineer
Your boiler has lost the ability to accurately measure the temperature of the water used for your radiators, causing it to shut down to prevent overheating.
Full guide for 0505
06 High Engineer
Your boiler is struggling to accurately measure the temperature of the water returning to it, which prevents the system from heating your home properly.
Full guide for 0606
07 High Engineer
Your boiler has detected an issue with the sensor that monitors the temperature of the exhaust gases, and it has stopped working for safety reasons.
Full guide for 07on the Alpha CD
Filling loopPressure relief valvePressure sensorPumpDiverter valvePrimary heat exchanger
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 Alpha 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