High Lockout
D.13 on Vaillant ecoTEC

Your boiler is having trouble moving hot water through the internal pipes, which usually means the circulation pump cannot start or is stuck.

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

Hot water circulation pump

What causes this fault?

This fault occurs when the boiler's internal pump fails to spin, meaning heated water cannot be moved toward your radiators or hot water tank. The most common reason is that the pump has become physically seized by a buildup of sludge or debris, or the electrical components inside the pump have reached the end of their lifespan.

This issue is frequently seen in autumn when the heating is turned back on for the first time after being idle all summer, which allows debris to settle and seize the pump.

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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