BoilerFaultCodesYour boiler is receiving a specific instruction from an external controller or thermostat telling it exactly what temperature to heat the water to.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: Flow target temperature from external analogue regulator terminal
What causes this fault?
This is not actually a fault, but an information message triggered when an external smart thermostat or plug-in controller takes over the boiler's temperature settings. It occurs when your external controls send a specific voltage signal to the boiler, telling it to override the manual dials and heat to a precise target. If your heating isn't working while this is displayed, the issue usually lies with a setting on your room thermostat or a communication error between the two devices.
DIY fix possible
Check if your external room thermostat or smart home hub is set to a very low temperatureEnsure your external controls have power and are connected to your Wi-Fi if applicableIncrease the temperature setting on your external thermostat to see if the boiler fires up
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A boiler cover plan would cover faults like D.9 — no call-out fees, no surprises.
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