Medium
S.54 on Vaillant ecoFIT Pure 435

Your boiler has temporarily stopped because it has detected that the water flowing through your radiators is not circulating or warming up as expected.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Waiting period: Low water pressure in the circuit (flow/return spread too large)

From this model's manual
Verified against the Vaillant Ecofit Pure 830 installation & service manual, page 33.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Check your radiators for trapped air and bleed them if they feel cold at the topEnsure all radiator thermostatic valves are fully openCheck that your external system pump (if fitted) is running and not seized

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