How much does it cost to fix boiler error code 4L?

Typical repair cost for the boiler 4L fault is £120-£200 including labour.

4L High

Boiler Fault Code 4L

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code 4L 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 an electrical fault with one of its main internal temperature sensors, causing the system to shut down for safety. (As reported on Ideal Maximiser SE)

Pick your boiler brand for the 4L fix

Ideal 4L 1 model

Source

Information for the 4L 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