BoilerFaultCodesTechnical description
Control thermostat overheat or pump failure cut-off devices operated. Faulty pump.
What causes this fault?
This fault occurs when the water inside the boiler reaches an unsafe temperature, triggering a safety switch to shut the system down. The most common reasons are a pump that has stopped circulating water or a blockage in the pipework that prevents heat from escaping the boiler. Just like an engine overheating, the boiler stops to prevent internal damage to its components.
This issue often appears when the heating is turned back on for the first time in autumn, as pumps can seize up after being idle throughout 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.