F.90 High

Vaillant F.90 Fault Code

Also written as F90 — same fault.

The Vaillant F.90 fault code means: your boiler has lost the digital connection to its hot water storage tank, preventing the two units from communicating properly.. It appears on 1 Vaillant model 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: Fault:Communication CheckthecableharnessfromtheproducttotheactoSTORmodule (PEBus). IftheproductistobeoperatedwithoutanactoSTORmodule,set D.092=0.
Typical repair cost £120-250 (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.90 fault code

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

Source

Vaillant F.90 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 27 April 2026