BoilerFaultCodesYour boiler's internal pump for hot water is stuck running at full speed, which usually means there is a communication error or a part is beginning to fail.
This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.
Technical description: Set speed internal DHW loading pump 100%
What causes this fault?
This fault occurs when the boiler's control board loses its ability to regulate the speed of the internal hot water pump, causing it to run at maximum power constantly. The most common reason is a communication failure between the pump and the main computer, often caused by a loose wiring connection or a failing electronic controller within the pump itself.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like 6C:100 — no call-out fees, no surprises.
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