Medium
ALL 21 on Sime Murelle Elite HE 35T System

Your boiler is having trouble reading the temperature for one of your heating zones, which may stop that specific area from warming up properly.

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

DELIVERY PROBE FAILURE FIRST MIXED ZONE

From this model's manual
Verified against the Sime Murelle Elite He Combi installation & service manual, page 32.
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

ALL 20View →ALL 22View →

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