Boiler Fault Code d.08

Also written as D08 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026

Fault code d.08 appears across 3 boiler brands and 31 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is currently receiving a signal from your thermostat that it is time to heat up, but there may be a loose connection or a fault in the communication between your wall controller and the boiler. (As reported on Glow-worm Energy7 Combi)