BoilerFaultCodesThe 3 most common faults
01
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 1502
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 2803
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 836 COMBI
Main PCB (Printed Circuit Board)Wiring HarnessFlue NTC SensorConnecting wiring harnessReturn NTC thermistor
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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