BoilerFaultCodesThe 6 most common faults
Your boiler is not receiving the signal to turn on, which usually means your external heating controls like the thermostat or programmer are not calling for heat.
Check that your room thermostat is turned up higher than the current room temperature.Ensure your heating programmer or timer is set to 'ON' or 'AUTO'.Check if the fuse for the heating system spur (usually a switch near the boiler) has blown or is turned off.
Your boiler is not receiving enough electrical power from the main supply to operate safely.
Check if other appliances in your home are flickering or behaving strangelyCheck your fuse box (consumer unit) for any tripped switchesContact your electricity provider to see if there is a known power fluctuations issue in your area
Your boiler is overheating because water isn't moving through the system properly or there isn't enough water inside.
Check that your system pressure is between 1 and 1.5 bar on the external gaugeEnsure all radiator valves and boiler isolation valves are fully openListen to see if the pump is vibrating or making a humming sound
Your boiler has got too hot and has shut itself down for safety, which is why your heating and hot water have stopped working.
Turn the boiler power off at the wall socket or fused spurAllow the boiler to cool down for at least 30 minutesPress the 'Reset' button (located at the bottom of the boiler) or turn the control knob to the 'R' position and back to 'On'
Your boiler is failing to light the gas burner properly and has shut down as a safety precaution.
Check that your gas emergency control valve is in the open positionCheck if other gas appliances (like a hob) are working to confirm gas supplyPress the reset button once to see if the boiler restarts
Your boiler has detected a problem with its internal temperature sensor, meaning it cannot accurately tell how hot the water is and has shut down as a safety precaution.
Full guide for Lights On Flash Onon the Baxi Solo 3
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