BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because it failed to light or detect a flame correctly and has entered a safety lockdown.
Check that your gas pre-payment meter (if applicable) has credit.Verify that other gas appliances in your home, like a hob, are working.Press the reset button once to see if the boiler restarts.
Your boiler has tried to light itself several times without success and has now locked itself out for safety.
Check that your gas emergency control valve is open and you have credit on your gas meterPress the reset button on the boiler control panel onceEnsure the external flue terminal is not obstructed by debris or snow
Your boiler's computer has encountered a memory processing error and cannot communicate correctly with its internal software.
Turn the boiler power switch offWait 30 secondsTurn the power back on to see if the system resets
Your boiler has detected that there is not enough water in the central heating system to operate safely.
Locate the filling loop, which is usually a flexible silver hose under or near the boiler.Open the small valves on the hose slowly until you hear water flowing and watch the pressure gauge.Close both valves tightly once the pressure gauge needle reaches between 1.0 and 1.5 bar.
Your boiler has failed to light after several attempts and has locked itself for safety.
Check that your gas supply is active and that other gas appliances work.Ensure there is credit on your gas meter if you have a pre-payment meter.Press the reset button on the control panel once to see if the boiler restarts.
Your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.
Allow the boiler to cool down for at least 30 minutesCheck that all radiator valves are open and not blocked by furnitureCheck if the system pressure is too low and top it up if necessaryPress the reset button on the control panel
on the Johnson Starley Optima E20
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 Johnson Starley 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