Medium
d3 on Alpha Intec S

Your boiler is struggling to detect the temperature of the water in your separate hot water tank, which is likely preventing the system from heating your tap water correctly.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

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

What the manual says

Manufacturer manual

Domestic hot water cylinder temperature sensor - Alpha Diverter valve kit fitted °C

Shared across the Alpha InTec 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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Related fault codes

d1View →d2View →

All 34 fault codes on the Intec S

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

010203040506081012151620242527293137384344464751d0d1d2d4d5d6d7d8d9

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