BoilerFaultCodesTechnical description
Is there 240V~ between yellow connection on overheat device and 10? Check overheat reset. If satisfactory replace overheat device.
What causes this fault?
This fault occurs when the boiler's internal water temperature exceeds a safe limit, triggering a safety sensor to cut the power. It is often caused by a failing pump that isn't circulating water quickly enough or a buildup of sludge and debris blocking the heat exchanger. The system shuts down completely to prevent internal components from melting or warping due to excessive heat.
This issue often surfaces during the first cold spell of autumn when the heating system is turned on after being dormant all summer, which can cause stuck pumps to fail.
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.