High
S.91 on Vaillant ecoTEC plus System

Your boiler has been accidentally set to a factory demonstration mode, which disables the heating and hot water functions until it is adjusted back to normal operation.

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

Maintenance: Demo mode

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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