F.326 High

Vaillant F.326 Fault Code

Also written as F326 — same fault.

The Vaillant F.326 fault code means: your boiler has detected that multiple internal valves or pumps are failing to respond, which means it cannot safely move water around the system to provide heating or hot water.. It appears on 3 Vaillant models in our database.

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: The hydraulicsensor and actuator test has detected at least two hydraulic components that are not working.
Typical repair cost £250-450 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Vaillant models that show the F.326 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Vaillant F.326 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026