BoilerFaultCodes Two red lights flash rapidly Low
Boiler Fault Code Two red lights flash rapidly
Also written as TWOREDLIGHTSFLASHRAPIDLY — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code Two red lights flash rapidly appears across 1 boiler brand and 3 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is currently set to a special testing mode used by engineers to check its performance, rather than operating in its normal heating mode. (As reported on Worcester Bosch Greenstar 25Si)
Pick your boiler brand for the Two red lights flash rapidly fix
Source
Information for the Two red lights flash rapidly 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