Medium
D.28 on Vaillant Atmomax

Your boiler is having trouble communicating with an external control or component connected to its secondary switch relay.

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

Switching accessory relay 2

Engineer required

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

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Related fault codes

D.27View →F.27View →F.70View →

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