BoilerFaultCodesThe 6 most common faults
01
Activate BCC High DIY-safe
Your boiler has recently had its main computer chip replaced and is waiting for you to restart it to complete the final setup.
What to try first
Locate the Reset button on the front control panel.Press and hold the Reset button for several seconds.Wait for the boiler to cycle through its startup sequence and check if the error clears.
02
0011 High Engineer
Your boiler has failed to light the flame after several attempts and has switched itself off for safety reasons.
Full guide for 001103
0001 High Engineer
Your boiler has switched itself off because it has become dangerously hot, likely due to a circulation blockage or a faulty sensor.
Full guide for 000104
Lockout flame signal High Engineer
Your boiler has stopped working because it cannot detect a flame, meaning it is currently unable to safely heat your home or water.
Full guide for Lockout flame signal05
Erroneous APS signal High Engineer
Your boiler has stopped working because it cannot confirm that waste gases are being safely pushed out through the flue, which is a necessary safety step before it can fire up.
Full guide for Erroneous APS signal06
Overheat thermostat activated High Engineer
Your boiler has switched itself off because it has become dangerously hot, likely due to a circulation problem or a faulty safety sensor.
Full guide for Overheat thermostat activatedon the Halstead Finest Gold
Burner Control Card (BCC)Ignition electrodeGas valvePrinted Circuit BoardNTC thermistorOverheat thermostat
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