Boiler Fault Code Green light flashing slowly

Also written as GREENLIGHTFLASHINGSLOWLY — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026

Fault code Green light flashing slowly 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 in standby mode and is working correctly, simply waiting for your thermostat or programmer to tell it that you need heat. (As reported on Potterton Prima 30B)