BoilerFaultCodesWorcester Bosch Light off Fault Code
Also written as LIGHTOFF — same fault.
The Worcester Bosch Light off fault code means: your boiler is currently sitting in standby mode because it hasn't received a signal from your thermostat or timer to start heating.. It appears on 10 Worcester Bosch models in our database.
Technical description: No boiler demand
What causes the Worcester Bosch Light off fault?
This occurs when the boiler is powered on and functioning correctly but is waiting for a 'call for heat' from your heating controls. The most common reason is that your room thermostat is set lower than the current room temperature, or your external timer is currently in an 'off' period. If your controls are turned up and the light remains off, it usually indicates a communication failure or a flat battery in your wireless thermostat.
This is frequently reported during the first cold spell of autumn when homeowners forget to turn their wall thermostats up or replace the batteries in their wireless controllers.
DIY fix possible
Check that your room thermostat is turned up higher than the current room temperature.Ensure your programmer or heating timer is set to 'ON' or 'Auto'.Replace the batteries in your wireless wall thermostat if the screen is blank.
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Gas Safe Register →Worcester Bosch models that show the Light off fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch Light off fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026