BoilerFaultCodesTechnical description
Check diagnostic code. Check external controls are calling for heat (also see note A sheet 1). Repair or replace as necessary.
What causes this fault?
This fault occurs when the boiler detects that water isn't moving through the heat exchanger as fast as it should. The most common reasons are a failing internal pump that can no longer push the water around or a large pocket of air trapped in the system blocking the flow.
This issue is frequently seen in autumn when the heating is turned back on for the first time after summer, as pumps can seize during long periods of inactivity.
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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