BoilerFaultCodesThe 5 most common faults
01
Power ON LED (Green) blinking High DIY-safe
Your boiler has detected that there is either not enough water inside the heating system or the sensor responsible for detecting flow is not operating correctly.
What to try first
Check your boiler's pressure gauge and ensure it is between 1 and 1.5 bar.If the pressure is low, locate the filling loop under the boiler to top up the system.Once the pressure is correct, restart the boiler to see if the blinking light stops.
02
Ignition Lock-out High Engineer
Your boiler has stopped working because it cannot light the flame required to produce heat or hot water.
Full guide for Ignition Lock-out03
OVERHEAT THERMOSTAT High Engineer
Your boiler has detected that it is getting too hot and has automatically switched itself off to prevent any damage or safety issues.
Full guide for OVERHEAT THERMOSTAT04
RED LED ON High Engineer
Your boiler has stopped working because it has failed to start properly or has become too hot and turned itself off as a safety precaution.
Full guide for RED LED ON05
Safety Lockout LED (Red) High Engineer
Your boiler has stopped working because it failed to start the burner, meaning you currently have no heating or hot water.
Full guide for Safety Lockout LED (Red)on the Halstead Ace High
Diverter valve microswitchFlow switchPressure sensorIgnition electrodeGas valvePCB
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