Low
d.41 on Vaillant Thermocompact

Your boiler is simply displaying the current temperature of the water returning to the system, which is a standard status update rather than a warning of a 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

Current return temperature (837/637 only) in °C

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.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Boiler cover options

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All 121 fault codes on the Thermocompact

Seeing a different code? Every code this model can display, in one place.

22.D24.D33.S35.SBurner lock out indicatord.00d.01d.02d.05d.07d.08d.10d.11d.21D.22d.23D.24d.25d.30d.33d.34d.35d.37d.40d.50d.60d.61d.64d.65d.67d.68d.69d.71d.72d.73d.75d.76d.80d.81d.82d.83Er.1Er.2Er.3Er.4Er.5Er.6Er.7Er.8Er.9Er.10Er.11Er.12Er.13Er.14Er.15Er.16Er.17F.00F.01F.10F.11F.20F.22F.23F.24F.27F.28F.29F.32F.33F.37F.41F.42F.43F.60F.61F.62F.63F.64F.65F.66F.67F22P1P2P3P11P12P13S.00S.01S.02S.03S.04S.05S.07S.08S.10S.11S.13S.14S.16S.17S.20S.21S.23S.24S.27S.28S.30S.31S.32S.33S.34S.36S.39S.52S.53S.54

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