How much does it cost to fix boiler error code F35?

Typical repair cost for the boiler F35 fault is £100-350 including labour.

F35 Medium

Boiler Fault Code F35

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code F35 appears across 1 boiler brand and 11 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 the quality of the electricity coming into your home, meaning the power supply is not stable enough for it to operate safely. (As reported on Ferroli Modena HE)

Pick your boiler brand for the F35 fix

Ferroli F35 11 models

Source

Information for the F35 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