BoilerFaultCodesZanussi oF Fault Code
Also written as OF — same fault.
The Zanussi oF fault code means: your boiler is in a standby or programming mode and thinks it has been told to stay switched off.. It appears on 3 Zanussi models in our database.
Technical description: PCB Programming - Off state
What causes the Zanussi oF fault?
This fault occurs when the boiler's internal computer has been set to a software-off state, often following a power cut or a manual adjustment in the programming menu. Instead of a mechanical breakdown, the boiler has essentially 'forgotten' it should be running and is stuck in a standby mode. In some cases, this can also happen if the main circuit board has a glitch and requires a professional reconfiguration.
DIY fix possible
Check that the boiler mode dial is turned to 'on' or the 'Hot Water and Heating' positionPress and hold the 'Reset' button for three secondsTurn the power to the boiler off at the fused spur switch, wait 30 seconds, and turn it back on
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Zanussi models that show the oF fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Zanussi oF fault code information on this page is sourced and cross-checked against the official Zanussi service / installation manuals for each affected model.
- Zanussi Ultra Combi manual (PDF)
- Zanussi Ultra Plus Combi manual (PDF)
- Zanussi Ultra System manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026