BoilerFaultCodesTechnical description
Overheat thermostat operated or faulty. Allow to cool. Check continuity across thermostat terminals.
What causes this fault?
This fault occurs when the water inside the boiler exceeds a safe temperature, triggering a safety switch to kill the flame. The most common reasons are a pump failure preventing heat from being carried away or a build-up of sludge and debris blocking the internal pipework.
This fault is more common in autumn when heating systems are first turned back on, as pumps can seize up after being inactive throughout the summer.
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.
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