Your boiler has switched itself off because it has detected that the internal temperature has become too hot and reached a dangerous level.

Over heat cut off activated, Flow probe not correctly thermal-connected or defective, appliance does not shut down

What causes this fault?

This fault occurs when the water inside the boiler gets too hot too quickly, triggering a safety sensor to shut the system 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 traps heat inside the unit.