738 Low

Viessmann 738 Fault Code

The Viessmann 738 fault code means: your boiler is connected to a smart heating control that hasn't been set up correctly in the system settings yet, so it is just waiting for the right instructions.. It appears on 1 Viessmann model in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Normal operation OpenTherm remote control connected but not configured
Typical repair cost £90-150 (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 738 fault code

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

Source

Viessmann 738 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