BoilerFaultCodesThe 6 most common faults
Your boiler has shut down because it has become too hot and needs to be safely reset after cooling down.
Why it happens: This fault occurs when the water inside the heat exchanger exceeds a safe temperature limit, triggering a safety cutout to prevent damage. The most common reasons include a failing circulation pump that isn't moving heat away quickly enough or a blockage in the system pipework. It can also be caused by a faulty internal sensor incorrectly reading the temperature.
Turn the boiler thermostat knob to the 'OFF' position.Wait at least 10 seconds for the system to acknowledge the reset.Turn the thermostat knob back to your desired temperature setting.
Your boiler is not receiving any electricity and has completely powered down.
Why it happens: This fault occurs when the boiler's electrical supply is completely cut off, preventing the control system from functioning. The most common reasons are a tripped circuit breaker in your fuse box, a blown internal fuse on the boiler's circuit board, or a failure of the printed circuit board itself.
Check if your home has had a power cut or if a fuse has tripped in your main consumer unit.Ensure the boiler's isolation switch (usually a white fused spur near the boiler) is turned on.Check if your prepaid gas or electricity meter has run out of credit.
Your boiler has detected that water is not moving through the system properly or there isn't enough water inside the unit to safely heat up.
Why it happens: This fault occurs when the boiler's internal sensors detect that heat isn't being carried away from the heat exchanger quickly enough, usually due to a lack of water flow. The most common reasons are a failed circulation pump that can no longer push water through the radiators, or a blockage such as a build-up of sludge or air in the pipework.
Check that your external heating system pressure is between 1 and 1.5 barEnsure all radiator valves and isolation valves are fully openGently bleed your radiators to remove any trapped air pockets
Your boiler has tried to start up several times but failed to light the flame, causing it to shut down for safety.
Why it happens: This fault occurs when the boiler's control system attempts to light the burner multiple times but fails to detect a stable flame. The most common reasons include a worn-out ignition spark, a faulty gas valve that isn't opening properly, or an issue with the sensor that confirms the fire is actually lit.
Check that your gas emergency control valve is open and you have credit on your meterPress the reset button or turn the control knob to 'O' and back to 'I'Check if other gas appliances in your home, like a hob, are working correctly
Your boiler's fan is failing to start or run correctly, which means the system cannot safely clear waste gases and will not fire up for your heating.
Why it happens: This fault occurs when the boiler's internal computer detects that the fan isn't spinning fast enough to safely push exhaust fumes out of the flue. The most common reason is that the fan motor has seized due to age or wear, or there is a build-up of debris blocking the fan's movement.
Full guide for FLASH FLASH ONYour boiler is not receiving enough electrical power from the main supply to operate safely.
Why it happens: This fault occurs when the electrical supply entering the boiler drops to a level where the electronic components can no longer function safely. It is usually caused by a wider problem with the local power grid or a failing main circuit board that can no longer process the incoming voltage correctly. In some cases, loose wiring or a faulty external socket can also cause this dip in electrical pressure.
Full guide for FLASH OFF FLASHon the Baxi Solo
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