BoilerFaultCodesBiasi Er 08 + Fault Code
Also written as ER08 — same fault.
The Biasi Er 08 + fault code means: your boiler's outside temperature sensor is either broken or sending a wrong signal, which affects how efficiently the heating adjusts to the weather.. It appears on 3 Biasi models in our database.
Technical description: Faulty external temperature probe NTC (if fitted)
DIY fix possible
Check if the boiler still provides heating and hot water (it should continue to work in a failsafe mode).Inspect the external sensor on the outside of your property for any obvious signs of damage or loose wires.Try resetting the boiler to see if the error clears.
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Biasi models that show the Er 08 + fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Biasi Er 08 + 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 7 July 2026