BoilerFaultCodesThe 6 most common faults
Your boiler is heating water too quickly or the heat isn't moving around your system fast enough, causing it to shut down to prevent overheating.
Check that all radiator valves are fully openEnsure the boiler pressure is between 1.0 and 1.5 bar on the gaugeBleed any air out of your radiators
Your boiler has paused because the water inside it is heating up much faster than it can be circulated around your home.
Check that your radiator valves are fully openEnsure the boiler pressure gauge is between 1.0 and 1.5 barCheck for any signs of air in the radiators and bleed them if necessary
Your boiler has shut down because it has detected that the water inside has become far too hot, likely due to a circulation problem.
Check that your radiator valves are fully openEnsure there is enough water pressure in the system by checking the gaugeBleed all radiators to remove trapped air pocketsReset the boiler using the reset button
Your boiler has detected that water is not moving through the system properly, which is often caused by low water pressure.
Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.If the pressure is too low, use the filling loop underneath the boiler to top it up.Bleed your radiators to remove any trapped air that might be blocking circulation.Restart the boiler to see if the fault clears.
Your boiler is heating up too quickly when producing hot water, causing it to shut down to prevent damage.
Check that the cold water mains stopcock and boiler isolation valves are fully openEnsure all hot water taps are fully turned on to allow sufficient flowCheck if the system pressure gauge is between 1 and 1.5 bar, and top up if necessary
Your boiler has detected that the water pressure is too low, which prevents it from heating your radiators and water properly.
Locate the filling loop (usually a silver braided hose with small lever valves) underneath the boiler.Slowly open both lever valves to allow water from the mains to enter the heating system.Watch the pressure gauge on the front of the boiler until it reaches between 1.0 and 1.5 bar, then close both valves tightly.
on the Baxi 400 Combi 2
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
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
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