Low
D.9 on Vaillant Atmomax

Your boiler is being told what temperature to run at by an external smart thermostat or control dial, rather than its own internal settings.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

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.

What the manual says

Manufacturer manual

Flow target temperature from external analogue regulator terminal

Shared across the range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Check your external wall thermostat or smartphone app to ensure the heating is turned up.Ensure any external control dials are not set to zero or 'off'.Monitor the boiler to see if the message disappears when the room reaches the desired temperature.

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Related fault codes

D.0View →D.90View →

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