BoilerFaultCodesThe 6 most common faults
01
Lockout High Engineer
Your boiler has stopped working because it couldn't safely ignite the flame after three attempts, often caused by a blockage in the gas supply or an issue with the air intake.
Full guide for Lockout02
Mains ON Only High Engineer
Your boiler has detected an internal fault that is preventing it from firing up, meaning you currently do not have heating or hot water.
Full guide for Mains ON Only03
Blocking High Engineer
Your boiler has switched itself off because it has detected an issue with its internal safety sensors or the electrical supply, and it needs a professional to investigate the cause.
Full guide for Blocking04
Earth Fault or Mains Reversal High Engineer
Your boiler has detected an issue with its electrical supply, meaning it cannot safely start up or operate your heating system.
Full guide for Earth Fault or Mains Reversal05
Overheat condition High Engineer
Your boiler has detected that it is getting too hot and has automatically shut itself down to prevent damage, requiring a professional check to ensure it is safe to use again.
Full guide for Overheat condition06
red light flashing High Engineer
Your boiler has failed to start after several attempts because it cannot detect a flame, so it has purposefully shut itself down for safety.
Full guide for red light flashingon the Potterton Profile 60E
Ignition leadSpark generatorGas valvePCBPrinted Circuit Board (PCB)Gas Valve
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 Potterton 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