How much does it cost to fix boiler error code A42?

Typical repair cost for the boiler A42 fault is £120-190 including labour.

A42 High

Boiler Fault Code A42

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 31 August 2026

Fault code A42 appears across 3 boiler brands and 8 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning The boiler's internal thermometer is sending an incorrect signal to the control board, preventing the system from heating your water correctly. (As reported on Ferroli Modena HE)

Pick your boiler brand for the A42 fix

Euroterm A42 1 model Ferroli A42 4 models Vokera A42 3 models

Source

Information for the A42 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