High
S.26 on Vaillant ecoTEC exclusive Combi

Your boiler's fan is attempting to spin, but the electronic control board isn't receiving the correct signal back to confirm it is working properly.

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.

What the manual says

Manufacturer manual

DHW mode: Fan overrun

From this model's manual
Verified against the Vaillant Ecotec Exclusive Combi installation & service manual, page 42.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This fault occurs when the boiler's central computer tries to start the fan but doesn't receive the required electronic pulse to confirm it is spinning at the right speed. It is usually caused by a physical blockage inside the fan's motor, a loose connection in the internal wiring, or a failure in the electronic components that monitor the fan's movement.

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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