BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because the internal fan, which safely exhausts gases, is unable to start or spin at the correct speed.
Why it happens: This fault occurs when the boiler's control board cannot detect the fan spinning at the speed required to safely clear waste gases from the system. The most common physical causes are a buildup of dirt or debris in the fan blades, a complete motor failure, or a loose electrical connection between the fan and the main circuit board.
Full guide for FAN LOCKOUTYour boiler has detected a faulty temperature sensor which means it can no longer accurately monitor how hot the water is getting.
Why it happens: This fault occurs when the internal temperature sensor fails to send a reliable signal to the main control board, often due to internal corrosion or electrical fatigue. Because the boiler can no longer track how hot the water is, it shuts down as a safety precaution to prevent the system from overheating. In some cases, the problem can also be caused by loose or damaged wiring that has broken the connection between the sensor and the brain of the boiler.
Full guide for THERMISTORYour boiler's main electronic control board has failed, which means the system cannot safely operate and has shut down.
Full guide for PCB FaultYour boiler has detected that it is not getting enough water or the water is not flowing through it properly, which usually happens if the system needs topping up.
Full guide for DRY-FIREYour boiler has stopped working because it failed to light the flame, which usually means it is not getting gas or there is a temporary safety blockage.
Full guide for IGNITION LOCKOUTYour boiler has automatically shut down because it has detected that it is getting dangerously hotter than it should be.
Full guide for OVERHEAT LOCKOUTon the Potterton Promax SL 24 Heat ErP
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 Potterton 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
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
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