BoilerFaultCodesThe 6 most common faults
01
26 High DIY-safe
Your boiler has stopped working because the water pressure inside the heating system has dropped too low to operate safely.
What to try first
Locate the external filling loop, which is usually a silver flexible hose connected to two valves under the boiler.Slowly open the valves to let water enter 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 turn the boiler off and back on again to reset the fault.
02
02 High Engineer
Your boiler is failing to light its internal flame, which means it cannot produce any hot water or heating.
Full guide for 0203
03 High Engineer
Your boiler has detected an issue with the electrical signal to the gas valve, meaning it cannot start the burner to heat your home or water.
Full guide for 0304
05 High Engineer
Your boiler has detected an internal computer error that is preventing it from starting up correctly.
Full guide for 0505
06 High Engineer
Your boiler has detected an internal computer error that is preventing it from operating correctly.
Full guide for 0606
13 High Engineer
The internal computer system that controls your boiler has experienced a glitch and can no longer safely operate.
Full guide for 13on the Alpha Cd50s Cd70s
Pressure relief valveFilling loopPressure sensorIgnition electrodeGas valvePrinted Circuit Board (PCB)
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