Low
P.00 on Vaillant ecoTEC Plus 938

Your boiler is currently running an automatic program to remove trapped air from the system, which usually happens during startup or after maintenance.

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

The heating circuit and hot water circuit are purged

From this model's manual
Verified against the Vaillant Ecotec Plus 826 installation & service manual, page 22.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This occurs when air has entered the heating system, often after the boiler has been drained, a radiator has been changed, or the system pressure has dropped. To prevent damage and ensure quiet operation, the boiler automatically runs a program to push this trapped air out of the internal pipework and heat exchanger.

This is most common in autumn when homeowners turn their heating back on for the first time or bleed their radiators to prepare for winter.

DIY fix possible

Wait approximately 6 to 7 minutes for the program to finish automaticallyEnsure your radiator valves are fully open to allow air to moveOnce the program ends, check if the water pressure is still within the green zone (1.0 to 1.5 bar)

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