Medium
db on Viessmann Vitodens 343-F WS4A

The boiler has lost its room thermostat reading for one heating zone, so it is controlling the heating by outdoor temperature instead, which usually keeps your home warm but may not match the room temperature exactly.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

Control mode without room influence - Room temperature sensor, heating circuit with mixer M2 shorted out

From this model's manual
Verified against the Viessmann/Viessmann Vitodens 343 F Ws4a 5592883 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

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

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Related fault codes

dCView →ddView →

All 59 fault codes on the Vitodens 343-F WS4A

Seeing a different code? Every code this model can display, in one place.

0F9A9b9C9F10182028303840485058929394A6A7b0b1b4b5b7b8bAbCbdbEbFC2CdCECFdAdddEE4E5E8E9EAEbECEdF0F1F2F3F4F8F9FAFCFdFEFF

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