Medium
50 on Atag iS System

Your boiler has lost communication with the hot water temperature sensor, meaning it cannot accurately heat your water.

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

T3 (DHW) sensor error (open, short circuit, or out of range)

Shared across the iS System 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

C154View →103View →104View →

All 18 fault codes on the iS System

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

1020406178105110111117118119129133151154180181

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