High Lockout
D.10 on Vaillant ecoTEC

Your boiler's internal pump is having trouble circulating water through the system, which is preventing your heating from working.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Status internal heating pump error

What causes this fault?

This fault occurs when the boiler's internal pump fails to spin or move water effectively through the system. The most common reasons are a mechanical failure of the pump motor, a build-up of debris or 'sludge' blocking the internal components, or a communication issue between the pump and the main control board.

This issue is frequently seen at the start of autumn when heating systems are turned back on after being idle all summer, as pumps can seize up 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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