High
d.35 on Vaillant Ecomax Condensing 600/800 series

Your boiler is struggling to switch between heating your radiators and providing hot water to your taps.

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

Diverter valve position (ecoMAX 800)

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

F.22View →

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