How much does it cost to fix boiler error code 9F:8?

Typical repair cost for the boiler 9F:8 fault is £120-280 including labour.

9F:8 Medium

Boiler Fault Code 9F:8

Also written as 9F8 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code 9F:8 appears across 1 boiler brand and 5 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your secondary heating circuit is not reaching the required temperature difference to operate correctly, likely due to a flow or sensor issue in that specific zone. (As reported on Viessmann Vitodens 200)

Pick your boiler brand for the 9F:8 fix

Viessmann 9F:8 5 models

Source

Information for the 9F:8 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026