Medium Warning
A0:1 on Viessmann Vitodens 300-W

Your boiler has lost communication with its remote control unit, meaning it may not be receiving the correct instructions to heat your home.

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.

Technical description

With Vitotrol 200 (automatic recognition)

What causes this fault?

This fault occurs when the link between your boiler and its wall-mounted control unit is broken. The most common reasons are a loose wiring connection at either end, damage to the communication cable, or a internal glitch in the control unit's electronic circuit board.

DIY fix possible

Check the thermostat or remote control unit is properly docked/mountedInspect the wiring between the boiler and the wall controller for any obvious loose connectionsTurn the boiler power off and back on to trigger a re-recognition of the remote unit

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Related fault codes

A0:2View →BCView →

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