BoilerFaultCodesTechnical description
Check continuity of water pressure switch and overheat 'stat. Check temperatures; if below 90°C replace stat, if above 90°C check CH/HW thermistors.
What causes this fault?
This fault occurs when the water within the heat exchanger reaches a dangerously high temperature, triggering a safety sensor to cut off the gas for your protection. The most common reasons for this are a lack of water circulation caused by a failing pump, a blockage in the pipework, or a sensor that has become faulty and is giving a false reading.
This issue often surfaces when you first turn your heating back on in autumn, as internal pumps can seize up after being idle during the summer months.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.