High
F.320 on Vaillant ecoTEC Plus 836

Your boiler's water pump is struggling to circulate water because it is blocked by debris or sludge, which will prevent your heating and hot water from working.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

Dirt or foreign bodies in the pump. The heating pump is blocked.

From this model's manual
Verified against the Vaillant Ecotec Plus installation & service manual, page 89.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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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