BoilerFaultCodesIdeal UF Fault Code
The Ideal UF fault code means: your boiler is currently stuck in a professional service mode used by engineers when they are replacing an internal valve.. It appears on 5 Ideal models in our database.
Technical description: Service mode / Diverter valve actuator replacement sequence step
What causes the Ideal UF fault?
This fault occurs when the boiler is manually placed into a specific testing mode used for replacing the motorized valve that switches between heating and hot water. It usually happens if an engineer has left the setting active by mistake or if the main control board has developed a software glitch that keeps it stuck in this maintenance sequence. Because the boiler believes it is being repaired, it will pause normal operation until the sequence is finished or cancelled.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Ideal models that show the UF fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal UF 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