High
E6 on Viessmann Vitodens 300-W

Your boiler's fan is failing to communicate correctly with the central control board, preventing the system from starting up for your safety.

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

Differential pressure sensor enables start (0.75 V across terminals X8.5 and X8.6), after approx. 51 seconds: Check fan cables and fan plug-in connections, check fan

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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