BoilerFaultCodesThe 6 most common faults
Your boiler is failing to light the gas flame despite several attempts, meaning your heating and hot water will not work.
Check if your gas supply is active by testing other gas appliances like a hob.Ensure your gas prepayment meter has sufficient credit.Press the 'Reset' button on the boiler control panel for 3 seconds.
Your boiler has shut down because it has reached an unsafe temperature and needs to cool down before it can be reset.
Check that all radiator valves are fully openEnsure the system pressure is between 1 and 1.5 barAllow the boiler to cool down and try pressing the reset button
Your boiler has stopped working because waste water cannot leave the system, likely due to a full or faulty pump or a blocked drainage pipe.
Check the external white plastic drainage pipe for any blockages or ice if it is cold outside.Ensure any visible condensate collection tanks are not full or overflowing.Gently pour warm water over the external pipe if you suspect it is frozen.
Your boiler has sensed that the air inside the system is getting dangerously hot and has shut down to protect itself.
Check all warm air vents (registers) throughout the house are open and not blocked by furniture.Inspect the air filter and clean it if it is dusty or clogged.Restart the boiler using the reset button once the unit has cooled down.
Your heater has automatically switched off because the air in the vents has become too hot, usually caused by blocked airflow or a lack of ventilation.
Check all heating vents and grilles around the house to ensure they are fully open and not blocked by furniture or curtains.Inspect the air filter on the unit and clean or replace it if it is clogged with dust.Ensure the intake and exhaust terminals outside your property are clear of debris, leaves, or snow.
Your boiler has switched itself off because the internal drain for waste water is full and cannot empty properly.
Locate the external plastic condensate pipe leaving your property.Check for any blockages at the end of the pipe or ice if the weather is freezing.Thaw any frozen sections using a hot water bottle or warm (not boiling) water.Restart the boiler using the reset button.
on the Johnson Starley C10d
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