1 second ON 1 second OFF Low

Biasi 1 second ON 1 second OFF Fault Code

Also written as 1SECONDON1SECONDOFF — same fault.

The Biasi 1 second ON 1 second OFF fault code means: your boiler is currently operating normally and is simply indicating that it is actively heating your radiators or hot water.. It appears on 4 Biasi 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: Boiler ON condition (function control in C.H. or D.H.W. position).
Typical repair cost £0 (including labour)

DIY fix possible

Check your thermostat to see if it is calling for heatTurn on a hot tap to confirm the boiler respondsNo action is required as this is a status indicator, not a fault

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Biasi models that show the 1 second ON 1 second OFF fault code

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

Source

Biasi 1 second ON 1 second OFF fault code information on this page is sourced and cross-checked against the official Biasi service / installation manuals for each affected model.

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