BoilerFaultCodesThe 6 most common faults
01
41 High DIY-safe
Your boiler is struggling to detect water moving through it, likely because the internal water pressure has dropped too low or a sensor is misreading the situation.
What to try first
Check your boiler control panel to see if the pressure gauge is below 1.0 bar.If the pressure is low, locate the filling loop (usually a silver braided hose under the boiler) and open the valves to let water in until the needle reaches 1.5 bar.Once the pressure is in the green zone, close the valves tightly and restart the boiler.
02
42 High DIY-safe
Your boiler has stopped heating because it cannot detect enough water moving through the system to operate safely.
What to try first
Check your boiler pressure gauge to see if it is below 1.0 bar.If the pressure is low, locate the filling loop under the boiler.Open the valves to allow water into the system until the gauge reads between 1.0 and 1.5 bar, then turn the valves off tightly.
03
❍❍❍❍ (DHW) High Engineer
Your boiler is failing to detect that you have turned on the hot tap, meaning it cannot provide hot water to your home.
Full guide for ❍❍❍❍ (DHW)04
❍❍❍❍ (Power) High Engineer
Your boiler has lost all electrical power and cannot operate at all.
Full guide for ❍❍❍❍ (Power)05
❍❍❍❍ (Flame) High Engineer
Your boiler has stopped working because it cannot detect that a flame has been successfully lit, likely due to a loose or disconnected internal wire.
Full guide for ❍❍❍❍ (Flame)06
0011 High Engineer
Your boiler is trying to start up but cannot successfully light the flame after five attempts, so it has locked itself out for safety.
Full guide for 0011on the Halstead Eden
Flow switchPressure sensorPressure relief valveDiverter valveCirculating pumpDHW flow turbine
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