Medium
A9 on Viessmann Vitodens 242-F FB2B

Your boiler is having trouble 'talking' to your room thermostat, which means it may not know when to turn the heating on or off.

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

Communication fault Open Therm device

From this model's manual
Verified against the Viessmann Vitodens 242 F B2ua installation & service manual, page 34.
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

A8View →F4View →

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