BoilerFaultCodesThe 6 most common faults
Your boiler has failed to light the gas flame after several attempts, meaning it cannot provide you with any heating or hot water until reset.
Check if other gas appliances, like your hob, are working to ensure you have a gas supply.Check that your gas meter has credit if you are on a prepay system.Press and hold the reset button for five seconds to see if the boiler restarts.
Your boiler has shut down because its internal temperature has gotten too hot, and it has triggered a safety cut-out to prevent damage.
Check that all radiator valves are fully openEnsure the system pressure is between 1 and 1.5 bar on the gaugePress the reset button once the boiler has had time to cool down
Your boiler has stopped working because the internal drainage pump cannot clear the water it produces, causing a backup that has shut the system down for safety.
Check if the external plastic drain pipe is frozen or blockedEnsure the pump unit is plugged in and receiving powerGently check the drain tube for any visible kinks or debris
Your boiler has sensed that the air it is heating is getting too hot and has shut down as a safety precaution.
Check all warm air vents in your home to ensure they are fully open and not blocked by furniture or curtains.Inspect the air filter on the unit; if it is dusty or clogged, slide it out and clean or replace it.Turn the boiler off at the fused spur switch, wait 30 seconds, and turn it back on to see if the fault clears.
Your boiler thinks it sees a flame even though it hasn't finished its startup sequence yet, so it has shut down for safety.
Full guide for E02Your boiler has stopped working because it cannot confirm that the fan is safely clearing waste gases from the system.
Full guide for E04on the Johnson Starley C16u
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