F.542 Medium

Viessmann F.542 Fault Code

Also written as F542 — same fault.

The Viessmann F.542 fault code means: your boiler has lost the connection to the temperature sensor that monitors the heat being sent to your radiators, which may cause your heating system to stop working correctly.. It appears on 1 Viessmann model 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: Lead break, flow temperature sensor, heating circuit 1 with mixer
Typical repair cost £120-200 (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.542 fault code

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

Source

Viessmann F.542 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