High
S.91 on Vaillant Home System

Your boiler is currently set to a 'showroom' demonstration mode, which allows the display to work but prevents the unit from actually heating your water or radiators.

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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Related fault codes

S.96View →S.97View →S.98View →

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