How much does it cost to fix boiler error code 3A?

Typical repair cost for the boiler 3A fault is £120-250 including labour.

3A High

Boiler Fault Code 3A

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 7 July 2026

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

Most common meaning Your boiler has detected an issue with its internal electrical protection system, meaning it has shut down to prevent potential damage to its electronic components. (As reported on Keston R-sm 20 FB)

Pick your boiler brand for the 3A fix

Buderus 3A 1 model Keston 3A 1 model Main 3A 1 model

Source

Information for the 3A 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 7 July 2026