High Lockout
E09 on Viessmann Vitodens 100-W

Your boiler has stopped working because the internal computer can no longer talk to or control the fan that helps clear exhaust gases.

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

Control unit fault. No communication with the fan.

What causes this fault?

This fault occurs when the boiler's main control board loses its electronic connection with the fan motor, meaning the system can no longer safely clear exhaust gases. The most common reason is a hardware failure within the fan's internal circuitry or a loose connection in the wiring harness that links the components together.

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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