Low
d.24 on Vaillant Home System

Your boiler is checking whether there is enough water pressure to run safely, but it hasn't yet confirmed if the pressure switch is active.

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

Status of the pressure monitor: off=Not switched, on=Switched

From this model's manual
Verified against the Vaillant Home System installation & service 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 the water pressure gauge on the boiler front or digital displayIf the pressure is below 1.0 bar, use the filling loop to top it up to 1.5 barEnsure all radiator valves are open and there are no visible leaks

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Related fault codes

F.22View →F.24View →d.05View →

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