BoilerFaultCodesThe 6 most common faults
01
3 05 High Engineer
Your boiler's internal computer has encountered a critical error and is unable to communicate with its own internal systems to function correctly.
Full guide for 3 0502
3 06 High Engineer
Your boiler's internal computer is experiencing a communication error and cannot operate, meaning you currently have no heating or hot water.
Full guide for 3 0603
6 10 High Engineer
Your boiler has detected that the internal water temperature has become dangerously high and has safely shut itself down to prevent damage.
Full guide for 6 1004
7 11 Medium Engineer
Your boiler is struggling to accurately read the temperature of the water returning from your heating system, which means it cannot heat your home efficiently.
Full guide for 7 1105
7 12 Medium Engineer
Your boiler is having trouble communicating with the temperature sensor for your secondary heating zone, which may prevent that part of your home from heating up properly.
Full guide for 7 1206
7 13 Medium Engineer
Your boiler is having trouble reading the water temperature in one of your heating zones, which may stop that specific area of your home from heating up correctly.
Full guide for 7 13on the Ariston Clas ONE System
Main PCBWiring harnessMain Printed Circuit Board (PCB)NTC temperature sensorCirculation pumpHeat exchanger
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 Ariston 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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