Medium
D.51 on Vaillant Atmomax

Your boiler's fan speed is slightly out of its normal operating range, meaning the system is struggling to regulate the air and gas mixture correctly.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Offset for maximum speed

Engineer required

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

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Related fault codes

F.32View →D.50View →

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