Boiler Fault Code 5 pulses (No light)

Also written as 5PULSESNOLIGHT — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026

Fault code 5 pulses (No light) appears across 1 boiler brand and 7 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler isn't broken; it has simply been left in a manual 'test mode' used by engineers, and needs to be switched back to its normal setting. (As reported on Worcester Bosch Greenstar 24i Junior)