12 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: CLAS HE
The fault code is already on your display
Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
Tap any card for details
Your boiler has detected that it is running too hot and has automatically shut down to prevent damage to its internal parts.
Your boiler has detected that water is not flowing through the system correctly, which is preventing it from heating your home properly.
Your boiler is struggling to pump water around your heating system, which is keeping it from warming up your radiators or taps.
Your boiler has detected that the water pressure inside the system is dangerously high, which can cause internal leaks or safety valve discharge.
Your boiler has lost the ability to measure the temperature of the water circulating through your radiators, so it has turned itself off as a precaution.
Your boiler has detected that the external temperature safety switch, often connected to underfloor heating, has cut the connection to the system.
Your boiler is struggling to accurately monitor the temperature of the water circulating through your radiators, so it has stopped working as a safety precaution.
Your boiler's electronic command center is experiencing a communication error and is unable to operate correctly.
Your boiler is having trouble communicating with the temperature sensor for your secondary heating zone, meaning it doesn't know how warm that specific part of your home is.
Your boiler has detected that the water inside the unit is getting too hot, so it has safely shut itself down to prevent damage.
Your boiler is struggling to push air through its internal system effectively, preventing it from safely lighting the flame.
Your boiler is having trouble communicating with the temperature sensor for your secondary heating area, which may cause that part of the home to struggle to heat up correctly.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes