BoilerFaultCodes Thermostat + Low
Boiler Fault Code Thermostat +
Also written as THERMOSTAT — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code Thermostat + appears across 1 boiler brand and 2 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is correctly receiving a signal from your thermostat that it needs to turn on, so this light simply indicates that your heating or hot water is currently in active mode. (As reported on Potterton Ultra 2 30 DV)
Pick your boiler brand for the Thermostat + fix
Source
Information for the Thermostat + 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