BoilerFaultCodesThe 6 most common faults
Your boiler has shut down because it has reached an excessively high temperature, triggering a safety switch to prevent damage.
Wait 30 minutes for the boiler to cool down completely.Ensure all radiator valves (TRVs) are fully open and there are no blockages.Press and hold the 'R' or Reset button for five seconds to restart the system.
Your boiler has stopped working because the water pressure is too low for the system to run safely.
Locate the filling loop (the silver flexible hose) underneath the boiler.Open the one or two taps on the loop slowly until you hear water flowing and the pressure gauge reaches 1.5 bar.Close the taps tightly and restart the boiler using the reset button.
Your boiler has detected that hot water isn't moving through the system properly, which usually means the pump is stuck or there is an airlock blocking the flow.
Check that your radiator valves are fully openBleed your radiators to remove any trapped airEnsure the boiler pressure is between 1.0 and 1.5 barReset the boiler to see if the fault clears
Your boiler is not receiving enough gas or is struggling to light the flame needed to heat your water and radiators.
Check that your gas emergency control valve is open and you have credit on your meter.If it is very cold outside, check if your white plastic condensate pipe has frozen and thaw it with warm water.Restart the boiler by turning the selector switch to the reset position for five seconds.
Your boiler has detected that water is struggle to move through the system properly before the burner ignites, often due to a blockage or a trapped air pocket.
Check that your boiler pressure is between 1.0 and 1.5 bar on the gaugeEnsure all radiator valves and isolation valves under the boiler are fully openGently bleed your radiators to release any trapped air from the system
Your boiler has switched itself off because it has gotten too hot, likely due to a blockage or air trapped in the system stopping the water from circulating.
Turn off the boiler and allow the system to cool down completely.Bleed all radiators using a radiator key to release trapped air.Check the boiler pressure gauge and top up to 1.5 bar if it has dropped.Press the Reset button on the front of the boiler for five seconds.
on the Baxi 400 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