BoilerFaultCodesThe 6 most common faults
Your boiler is failing to light the gas or stay lit, which has caused it to shut down for safety.
Check if other gas appliances like your cooker are working to ensure gas is being supplied to the house.If it is freezing outside, check if your white plastic condensate pipe is frozen and thaw it with warm water.Press and hold the 'Reset' button for five seconds to see if the system restarts.
Your boiler has shut down because it has detected that the water inside is Getting too hot, which is a safety feature to prevent damage.
Check if any radiator valves are closed and open them fullyEnsure your system pressure is between 1 and 1.5 bar on the gaugePress the 'Reset' button for five seconds to restart the boiler
Your boiler has lost its connection to your thermostat or remote heating controller, meaning it cannot receive instructions to turn the heating on.
Check and replace the batteries in your room thermostat or remote control unit.Ensure the heating controller is within range of the boiler and has not been moved.Turn the power switch to the boiler off and back on again to restart the radio connection.
Your boiler's internal computer has encountered a critical electronic software or hardware error that is preventing it from running safely.
Full guide for F0Your boiler's internal fan isn't spinning fast enough to safely clear away exhaust fumes, causing the system to shut down for your protection.
Full guide for C1Your boiler is temporarily locked out because it cannot detect water movement or pressure change when the internal pump starts up.
Full guide for CEon the Worcester Bosch Greenstar 25Si Compact ErP
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 Worcester Bosch 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