Medium
A8 on Worcester Bosch Greenstar 42CDi

Your boiler has lost its connection to your room thermostat or control panel, meaning it no longer knows when to turn your 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

Break in communication to TD200 or/and RT10.

From this model's manual
Verified against the Worcester Bosch/Worcester Bosch Greenstar Cdi Classic 2012 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

A7View →

All 12 fault codes on the Greenstar 42CDi

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

A1A7b1C6E2E9EAF0F7FAFd

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