BoilerFaultCodesIdeal 9.1.12 Fault Code
Also written as 9112 — same fault.
The Ideal 9.1.12 fault code means: your heat pump has stopped working because a sensor that measures the water temperature returning from your home has developed a fault.. It appears on 1 Ideal model in our database.
Technical description: Outdoor Unit, Return Thermistor (Tw_In)
What causes the Ideal 9.1.12 fault?
This fault occurs when the heat pump's control system loses the ability to accurately measure the temperature of the water returning from your radiators. This is usually caused by the internal electrical components of the sensor failing or the wiring becoming damaged, which prevents the unit from knowing how much heat is needed. Because the system can no longer safely monitor the heating cycle, it shuts down to prevent damage to the compressor.
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 9.1.12 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal 9.1.12 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