BoilerFaultCodesThe 6 most common faults
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AL28 Engineer
Temperature differential inverted (return sensor temperature higher than thermistors flowsensor temperature)
Full guide for AL28Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Pro 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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