BoilerFaultCodesThe 6 most common faults
Your boiler has detected that there is not enough water circulating through the system, which could be caused by a leak or a pump that has stopped working.
Check for any visible water leaks around the boiler or radiatorsEnsure the system pressure is topped up to 1.5 bar using the filling loopTry restarting the boiler to see if the pump clears itself
Your boiler has shut down because a sensor has detected that the water inside is getting too hot, or there is a problem with the circulation or pressure preventing safe cooling.
Check the pressure gauge on the front of the boiler; if it is below 1 bar, top it up to 1.5 bar using the filling loop.Ensure all radiator valves are fully open to allow water to circulate freely.Press and hold the reset button for five seconds to see if the system restarts once cooled.
Your boiler has stopped working because it cannot light the burner, which is usually caused by a problem with the gas supply or the ignition system within the unit.
Check if your gas meter has credit and that the main gas lever is turned on.Try to relight other gas appliances, like a hob, to confirm there is a gas supply to the house.Press and hold the reset button for five seconds once gas supply is confirmed.
Your boiler is checking if the pump is working correctly to move water through the system, but it has not detected the required flow.
Check that your radiators are bled and all radiator valves are fully openEnsure the boiler pressure is between 1 and 1.5 bar on the pressure gaugeRestart the boiler to see if the internal pump test clears the error
Your boiler has detected that the water inside is getting too hot and has shut itself down as a safety precaution.
Check that your radiator valves are openEnsure the system pressure is between 1 and 1.5 bar on the pressure gaugeTurn the boiler off and back on again to attempt a reset
Your boiler has shut down because a safety sensor has detected that the internal water temperature is too high or the sensor itself has failed.
Turn the boiler off and wait 20 minutes for it to cool downCheck that your radiator valves are open and not blockedPress the reset button and restart the boiler
on the Worcester Bosch 35 RSF
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