BoilerFaultCodesViessmann E09 Fault Code
The Viessmann E09 fault code means: your boiler has stopped working because the internal computer can no longer talk to or control the fan that helps clear exhaust gases.. It appears on 1 Viessmann model in our database.
Technical description: Control unit fault. No communication with the fan.
What causes the Viessmann E09 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 fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Viessmann models that show the E09 fault code
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Source
Viessmann E09 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026