BoilerFaultCodesTechnical description
Indicates the overheat thermostat has operated. Fault will be rectified by allowing the boiler to cool and turning the selector switch to the reset position.
What causes this fault?
This fault occurs when the water inside the boiler exceeds a safe temperature, causing the system to shut down to prevent damage. The most common reasons are a pump failure that stops water from moving or a blockage in the heat exchanger that restricts flow. It can also be caused by a faulty internal sensor that is incorrectly reporting the temperature.
This fault is frequently seen when the heating is first turned on after summer, as the internal pump can often seize or stick during long periods of inactivity.
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.