High
604 on Ariston Alteas One

Your boiler's fan is running too slowly, which prevents the system from safely starting up to provide heating and hot water.

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.

Technical description

CLAS HE RE-Combi EvoE-System EVOClas HE evo CombiClas HE evo System

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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