BoilerFaultCodesThe 6 most common faults
01
Activate BCC High DIY-safe
Your boiler has had a new computer chip installed and is currently waiting for you to simply acknowledge the change so it can start working again.
What to try first
Locate the reset button on the front control panelPress and hold the reset button firmly for 2 to 3 secondsWait a moment for the boiler to cycle and attempt to fire up
02
0011 High Engineer
Your boiler has tried to light the flame five times but failed, so it has safely shut itself down to prevent a build-up of unburnt gas.
Full guide for 001103
0001 High Engineer
Your boiler has detected that it has become too hot and has automatically switched itself off to prevent any damage.
Full guide for 000104
Lockout flame signal High Engineer
Your boiler is failing to ignite or stay lit because it cannot detect a flame, meaning you currently have no heating or hot water.
Full guide for Lockout flame signal05
Erroneous APS signal High Engineer
Your boiler is struggling to detect that the internal fan is venting air properly, which prevents it from igniting safely.
Full guide for Erroneous APS signal06
Overheat thermostat activated High Engineer
Your boiler has automatically shut down because it has detected that its internal water temperature has become dangerously high.
Full guide for Overheat thermostat activatedon the Halstead Finest 120
Boiler Control Circuit (BCC) boardIgnition electrodeGas valvePCBNTC ThermistorPrimary 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 Halstead 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