How much does it cost to fix boiler error code neon '12' illuminated?

Typical repair cost for the boiler neon '12' illuminated fault is £90-180 including labour.

neon '12' illuminated High

Boiler Fault Code neon '12' illuminated

Also written as NEON12ILLUMINATED — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code neon '12' illuminated appears across 1 boiler brand and 1 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 that a vital internal temperature sensor is disconnected or has failed, preventing it from heating your home safely. (As reported on Ideal Classic NF)

Pick your boiler brand for the neon '12' illuminated fix

Ideal neon '12' illuminated 1 model

Source

Information for the neon '12' illuminated 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