How much does it cost to fix boiler error code 99?

Typical repair cost for the boiler 99 fault is £150-300 including labour.

99 High

Boiler Fault Code 99

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 31 August 2026

Fault code 99 appears across 5 boiler brands and 13 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler's control panel has lost its connection to the main internal computer, causing the system to stop functioning because it cannot receive instructions. (As reported on Johnson Starley C16u)

Pick your boiler brand for the 99 fix

Alpha 99 4 models Biasi 99 2 models ECA 99 1 model Johnson Starley 99 5 models Navien 99 1 model

Source

Information for the 99 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 31 August 2026