BoilerFaultCodesTechnical description
Stepper motor fault (Diverter valve)
What causes this fault?
This fault occurs when the motor that controls your boiler's internal flow valve becomes jammed or suffers an electrical failure. The most common reason is that small bits of debris or sludge from the heating system have physically blocked the valve, putting too much strain on the motor and causing it to fail.
This issue is often noticed in autumn when the heating is turned on for the first time after summer, as the valve may have seized in the hot-water-only position due to lack of movement.
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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