Medium
A15 on Ariston Clas One

Your boiler is struggling to communicate with your room thermostat, meaning it doesn't know when to turn your heating on or off.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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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

ExternalTimer/Room Thermostat

Engineer required

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

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Related fault codes

A16View →

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