High
A8 on Worcester Bosch 537i

Your boiler's internal control system has lost its ability to talk to the external thermostat, meaning it doesn't know when to turn the heating on.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Communication interrupted.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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