BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.
Why it happens: This fault occurs when the water pressure inside your heating system drops below a safe level, causing the boiler to shut down to prevent internal damage. The most common reasons are a slow leak from a radiator valve or pipework, or air being released from the system through the radiators or an internal auto-air vent.
Locate the filling loop (usually a silver braided hose with two blue-handled valves) underneath the boiler.Slowly open both valves until you hear water entering the system.Watch the pressure gauge and close both valves firmly once the needle reaches between 1.0 and 1.5 bar.
Your boiler has switched itself off because it has detected that the water inside the system has become too hot to operate safely.
Ensure all radiator valves are fully open to allow water to flow.Check that the system pressure is between 1 and 1.5 bar on the gauge; top up if necessary.Turn the boiler off and on again or hold the 'Reset' button for 5 seconds.
Your boiler has detected that the water pressure is too low for it to operate safely, which is why it has stopped working.
Locate the filling loop (usually a silver flexible hose) underneath the boiler.Slowly open the one or two taps/levers on the filling loop until you hear water flowing.Watch the pressure gauge and close the taps when the needle reaches between 1 and 1.5 bar.
Your boiler has detected that water is not moving through the system properly, which is causing it to shut down to prevent overheating.
Check that your system pressure is between 1 and 1.5 bar on the gaugeEnsure all radiator valves and isolation valves under the boiler are fully openGently bleed your radiators to remove any trapped air pockets
Your boiler has lost its flame while it was running, meaning it cannot stay alight to provide heating or hot water.
Check that your gas supply is active (e.g., check other gas appliances or your meter credit)Restart the boiler by pressing the reset button for five secondsCheck if the condensate pipe (the plastic pipe leading outside) is frozen or blocked
Your boiler has failed to light because it cannot get enough gas or cannot detect the flame used to heat your water.
Check that your gas prepayment meter has credit and is turned on.Ensure other gas appliances in your home, like a hob, are working correctly.Press and hold the 'R' or Reset button for five seconds to restart the boiler.In winter, check that the white pipe leading outside (condensate pipe) isn't frozen.
on the Baxi 600 Combi (range)
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 Baxi 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