4 (Flashing Light) Low

Ferroli 4 (Flashing Light) Fault Code

Also written as 4FLASHINGLIGHT — same fault.

The Ferroli 4 (Flashing Light) fault code means: your boiler is currently in standby mode and is working exactly as it should while waiting for a signal from your thermostat to provide heating.. It appears on 9 Ferroli models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Central heating standby

DIY fix possible

Check your room thermostat is set to a higher temperature than the current room temperatureEnsure your heating timer or programmer is currently in an 'ON' periodVerify the central heating dial on the boiler front panel is not turned to the off position

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Ferroli models that show the 4 (Flashing Light) fault code

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

Source

Ferroli 4 (Flashing Light) fault code information on this page is sourced and cross-checked against the official Ferroli service / installation manuals for each affected model.

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