BoilerFaultCodesThe 6 most common faults
01
110 High DIY-safe
Your boiler has switched itself off because it has detected an overheating issue to keep the system safe.
What to try first
Check that your radiator valves are open and not turned to zero.Ensure your boiler pressure is between 1 and 1.5 bar on the gauge.Perform a 'Reset' by turning the selector knob to the 'R' position for five seconds.
02
125 High DIY-safe
Your boiler has detected that water is not moving through the system properly, which is causing it to shut down to prevent overheating.
What to try first
Check that your system pressure is between 1 and 1.5 bar on the front gauge.Ensure all radiator valves and isolation valves under the boiler are fully open.Bleed your radiators to remove any trapped air pockets.
03
15 High Engineer
Your boiler's main internal computer has developed a communication fault and is unable to run the system safely.
Full guide for 1504
135 High Engineer
Your boiler’s main control board has encountered an internal electronic error or a loose connection, preventing the system from running safely.
Full guide for 13505
28 High Engineer
Your boiler has detected a problem with the sensor that monitors the temperature of the exhaust gases, causing the system to shut down for safety.
Full guide for 2806
40 High Engineer
Your boiler has detected an issue with the sensor that monitors the temperature of the water returning from your radiators.
Full guide for 40on the Baxi 825 Combi
Safety Overheat ThermostatCirculation PumpTemperature Sensor (NTC)Water Pressure SensorAutomatic Air VentMain PCB (Printed Circuit Board)
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
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