FAILURE TO LIGHT High

Johnson Starley FAILURE TO LIGHT Fault Code

Also written as FAILURETOLIGHT — same fault.

The Johnson Starley FAILURE TO LIGHT fault code means: your boiler is not firing up because it isn't receiving the correct signal from your thermostat or internal controllers to start the heating process.. It appears on 1 Johnson Starley model in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: External controls, port valves, or programmer issues. Includes checks for 230V on display SL and potential display or PCB replacement.
Typical repair cost £120-350 (including labour)

DIY fix possible

Check that your room thermostat is turned up higher than the current room temperature.Ensure your programmer or heating clock is set to an 'ON' period.Replace the batteries in your wireless room thermostat if the display is blank.

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Johnson Starley models that show the FAILURE TO LIGHT fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Johnson Starley FAILURE TO LIGHT fault code information on this page is sourced and cross-checked against the official Johnson Starley service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026