BoilerFaultCodesIdeal 85 Fault Code
The Ideal 85 fault code means: your boiler is struggling to light or keep a flame burning correctly because the gas and air mixture isn't balanced.. It appears on 2 Ideal models in our database.
Technical description: Flame detection and mixture
What causes the Ideal 85 fault?
This fault occurs when the boiler's internal sensor fails to detect a consistent flame after it tries to ignite. The root cause is usually a breakdown in the balance between gas and air, or a worn-out sensor that can no longer tell the control board that the fire is safely lit.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Ideal models that show the 85 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal 85 fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026