BoilerFaultCodes 661 High
Boiler Fault Code 661
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 661 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 is not receiving the correct electrical voltage needed to run, likely due to an issue with your home's power supply or a failing internal circuit board. (As reported on Worcester Bosch WR325 RSF)
Pick your boiler brand for the 661 fix
Source
Information for the 661 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