BoilerFaultCodesThe 6 most common faults
Your boiler has become too hot and has automatically shut itself down as a safety precaution.
Why it happens: This fault occurs when the water inside the boiler exceeds a safe temperature limit, causing the safety sensor to cut the power. The most common reasons are a pump failure that prevents water from moving through the system or a build-up of sludge and debris blocking the internal pipework.
Locate the reset button on the control panel, usually hidden under a small plastic cap or recessed.Press the reset button firmly to clear the lockout.Check that your radiator valves are open and that the pump is running to prevent it from overheating again.
Your boiler has shut down because it has either become too hot or detected that dangerous exhaust fumes are not escaping correctly through the chimney.
Why it happens: This fault occurs when the boiler's internal temperature or flue gases exceed safe limits, triggering a safety shut-off to protect your home. The most common reasons are a failure in the pump preventing water from moving through the system or a blockage in the chimney preventing exhaust fumes from escaping.
Full guide for Red LED (Illuminated)Your boiler has become too hot and has automatically switched itself off to prevent damage, meaning you currently have no heating or hot water.
Full guide for Red LED (Overheat)Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.
Full guide for Red LED illuminated (Overheat)Your boiler has become too hot and has automatically switched itself off as a safety precaution.
Full guide for Red LEDYour boiler has sensed a problem with the dangerous exhaust gases escaping, so it has automatically shut itself down to keep your home safe.
Full guide for Red LED (TTB)on the Potterton Kingfisher MF 40-100
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