Low
D.1 on Vaillant Atmomax

Your boiler is currently cooling itself down after providing heating, which is a normal operating status rather than an actual fault.

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

Water pump overrun – time for heat mode

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

Wait for the timer to finish (usually 2-5 minutes)Check that your room thermostat is not set too highEnsure radiator valves are open to allow heat to dissipate

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Boiler cover options

Avoid the next call-out bill

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Related fault codes

D.0View →D.2View →

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