BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working and locked itself out because it failed to light or stay lit correctly.
Why it happens: This fault occurs when the boiler's control board fails to detect a stable flame after several attempts to ignite. The most common reasons are a worn-out ignition spark that can no longer light the gas or a dirty sensor that cannot 'see' the flame even if it is burning. In some cases, it may be caused by an inconsistent gas supply or a failing gas valve that isn't opening correctly.
Check if your gas supply is turned on (try another gas appliance like a hob).Press the reset button once to see if the boiler restarts.Ensure your condensate pipe has not frozen if it is a very cold day.
Your boiler has no power going to it at all, meaning the screen is blank and it won't respond to any commands.
Why it happens: This fault occurs when the boiler's electrical heartbeat is interrupted, preventing the control system from waking up. The most common reason is a blown internal fuse or a failed main circuit board that can no longer distribute power. Occasionally, this is triggered by an external issue like a tripped circuit breaker or a faulty transformer failing to convert the voltage correctly.
Check if your main electrical consumer unit has trippedEnsure the fused spur switch next to the boiler is turned onCheck the 3-amp fuse inside the boiler's wall switch
Your boiler has stopped working completely and entered a safety lockout mode to prevent further issues.
Why it happens: This fault occurs when the boiler has tried to ignite several times but failed to establish or detect a stable flame. The most common reasons are a lack of gas reaching the burner, a worn-out ignition spark, or the internal control board failing to recognize that the boiler has successfully lit.
Locate the reset button on the control panelPress and hold the reset button for several secondsWait for the boiler to attempt to restartCheck that your gas pre-payment meter (if applicable) has credit
Your boiler has stopped working because it can no longer accurately read the temperature of the water inside it.
Full guide for Pulse Red (1 flash)Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.
Full guide for Pulse Red (2 flashes)Your boiler is failing to ignite the flame needed to produce heat and hot water.
Full guide for Pulse Red (4 flashes)on the Potterton Envoy
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