F.546 Medium

Viessmann F.546 Fault Code

Also written as F546 — same fault.

The Viessmann F.546 fault code means: a sensor responsible for measuring the water temperature in your second heating zone is reporting a fault, which may prevent that specific part of your heating system from warming up correctly.. It appears on 4 Viessmann models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Short circuit, flow temperature sensor, HC2 with mixer
Typical repair cost £120-£210 (including labour)

Engineer required

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

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Viessmann models that show the F.546 fault code

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

Source

Viessmann F.546 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 7 July 2026